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prey on Sunday last. It is deeply to be re-most of whom we may class Mr. George Rennie, ment and certain in its results. The modelling gretted that such a loss should have occurred, who died on the 30th March, at the age of 75. and cutting-out of many objects in glass and and still more so that the preventive measures Mr. Rennie's name is inseparable from many im- enamel have hitherto been effected by instruadopted fell so far short of the actual require- portant improvements, especially docks, har-ments only admitting of the production of one ment. All had gone so well hitherto that bours, and breakwaters. To him is due piece at a time, and, consequently, the condiperhaps it was thought that the Palace never the credit of having made the first tions of economy, which require that dupliwould be subject to such an accident, but pre- surveys for the Liverpool and Manchester cates should not only be exact counterparts paration should always be made for every con- Railway. Next comes Mr. C. Wye Williams, one of another but also be produced one after tingency, so that in any emergency ample who died a few days after Mr. Rennie, and the other in a continued stream, as it were, means of extinction should be at hand. As it whose name recals a vast amount of research have been very inadequately fulfilled. The is, the work of years and the worth of many and practical information upon the combustion object of the little instrument in the annexed thousand pounds was swept away in a few of coal. Upon this subject Mr. Williams be-cut, which is the invention of M. Coutéat, an hours, and about one-third of the people's came an unquestionable authority, and in his ingenious mechanician of Paris, is to provide palace is a ruin. It is a satisfaction, however, treatise thereon, he has left a rich legacy to a method for cutting out with that rapidity to think that the whole building and its con- the profession which at the ripe age of 87 he only obtainable by the aid of machinery a tents were not sacrificed; their preservation is ceased to adorn. On the 6th of March, Dr. number of articles consecutively. The pecuperhaps only due to the course of the wind, Whewell died from the results of an accident liarity which distinguishes this apparatus from which blew in a direction favourable for the while riding; he was a man whose mind was those which have been constructed on a larger saving of the greater portion of the building. cast in no ordinary mould, and whose writings scale for more refractory and obdurate mateIt must be some time before the tropical de- at one time adorned our own pages. His his- rials than enamel and glass, consists in the partment can present its former beautiful tory of the inductive sciences, with its equal, circumstance that the frame which holds the appearance. In the mean time, and while the the philosophy of the inductive sciences, are matrices is movable upon a hinge joint, thus work of reconstruction is progressing, let it be works from which his fame must ever be re- permitting the finished piece to be removed carefully seen that no arrangement of flues is flected. Geology has suffered a loss in the with greater facility. adopted that may lead to another such deplor-person of Mr. Charles Maclaren, who died on able accident. One thing appears to us very the 10th of September. Later on early in certain, and that is, if the sash-bars had been December, the Royal Scottish Society of Arts of iron instead of wood the fire would not have lost their president, Mr. Alexander Bryson. injured the roof, except in the immediate locality Art and medicine have suffered greatly, many of the big tree. Light iron sash-bars might losses having occurred in these departments; have been introduced without too great a but there are numbers yet awaiting to recruit weight being brought upon the roof; but par- the ranks of science, as they become simony would have wood, and now the penny. thinned by death, and, although the struggle to wise and pound-foolishness of the arrangement fame is often a long and a weary one, true is apparent. It is, however, satisfactory to talent must ever be victorious, and with an learn that the receipts of the Crystal Palace ample stock of this everywhere around us, we Company will not be diminished by the fire, may hope that the year just born will be in which has left intact the whole of that portion no whit behind the year just closed in the of the Palace devoted to the Christmas amuse- matter of scientific progress. ments. Indeed, the attendance has greatly increased owing to the curiosity of the people to look upon the ruined portion of their palace. Communication by rail with the building, however, has been greatly retarded the last few days, owing to the heavy fall of snow, which has stopped the traffic in some parts.

RAILWAYS.

Apropos of railway traffic it may not be uninteresting here to summarise its results during the past year. We therefore give some interesting statistics from the annual return relating to the railways of the United Kingdom, which has just been issued by the Board of Trade. From that return it appears that during the last year 165 persons were killed and 971 injured on railways in England; 39 were killed and 143 injured on lines in Scotland; and 17 were killed and 18 injured on lines in Ireland. Total on the railways of the United Kingdom: killed, 221; injured, 1,132. There were 112 collisions, by which 49 persons were killed and 1,106 injured. The total number of passengers carried on the English and Welsh lines amounted to 216,693,538, on an aggregate length of 9,251 miles. There were 4,485,864 trains run, and these travelled more than 114,000,000 miles. The receipts from all sources were £30,166,311. The results were an increase of 361 over the mileage of 1864, and of nearly a million and a half on the receipts. Scotland showed an increase of revenue to the extent of £220,432, and Ireland £155,455. The total receipts on the railways of the three kingdoms were £35,890,113, or an increase of £1,874,549 over the revenue of the previous year. There was, however, also an increase in the working expenditure, which left £18,602,582 as the nett receipts of the year. The paid-up capital reached the enormous sum of £357,657,046, or £25,000,000 more than in 1864. The authorised capital exceeds £576,000,000, being £55,000,000 more than it was in the year preceding.

CONCLUSION.

PUNCHING GLASS AND ENAMEL.

WE

THEREVER hand labour is employed constructive or commercial value it is only by for the production of any article of frequent comparisons with a standard gauge or pattern and numerous successively tentative processes and examinations that the one can

be pronounced to be even an approximate

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The merits of the machine will be apparent by inspecting the engravings. Fig. 1 represents an elevation with a small portion in section, and fig. 2 a horizontal sectional plan along the line 1-2 in fig. 1. The apparatus has very much the appearance of an ordinary punching press. The stand or upright A, which is cast in one piece with the plate A', is fixed by bolts to a beam or balk T. The plate A carries the matrices, the frame of which is mounted upon the hinge c, and is supported by a small disc bearing upon a spiral spring enclosed in the tube D, and the pressure of which can be regulated at pleasure by means of the screw v. The frame C, containing the matrices (see figs. 1 and 2), is held immovable during the operation by the catch h, which is mounted upon a pivot, and can be caused to move by using the small lever e. catch h, until the latter is set in motion by the The frame is held in its place by a small spring, which presses constantly upon the

lever e. The stock of the instrument E contains as many punches as there are matrices, whose motion is maintained perfectly vertical and uniform. The punches being raised and the objects placed upon the matrices, the lever H is turned half round, and, as can be seen without further description, the operation is accomplished. The workman then lowers the level e, which releases the frame holding the matrices from the catch pressing against it, and, by pulling over the handle L, the frame is caused to take the position shown by the dotted lines in fig. 1. This alteration in the position of the frame allows the punched particles to fall at once clear of the machine. It is obviously a matter of accommodation to make the form of the punches round or any other shape that may be desired, and also their number may be increased and diminished according to the particular circumstances of the case. That the introduction of machinery for the purpose of effecting those branches of mechanical industry previously performed by hand labour has a limit there is very little doubt, but where that limit is it is impossible to say. It must not be supposed that the employment of machine instead of hand labour accomplishes everything that could be desired. On the contrary, there is no machine in the world which can compete, for accuracy of finish, with the best descriptions and specimens of hand labour; but, on the other hand, it possesses the advantages of rapidity and, what is much more valuable, of certainty. One may safely trust to a machine to do its duty, but one cannot always trust to a workman. The one, so long as it is in order, cannot make a mistake; the other very frequently does, often unwittingly.

VENTILATION OF THE PARIS
EXHIBITION.

duplicate of another. Not only is a large amount of time consumed in endeavouring to We cannot conclude our retrospective glance obtain this similarity, but it requires the exerwithout some allusion to those workers in the cise of patience and temper to a degree with cause of science who have been taken from which few workmen are endowed. The introamong us during the past year. The ranks of en- duction of machinery has rendered what was gineering have been thinned by the loss of'seve- formerly a toil, and, at the best, but an inral members of the profession, among the fore-different success, a matter of easy accomplish-who will visit this marvellous erection during

F the thousands, or, probably, we may

Osay with more correctness, of the millions,

these subterranean galleries, a canard was
going the round of the Parisian papers a short
time ago, which was a little amusing, although
very ridiculous. It asserted that the Burgo-
master of Brussels, when inspecting the under-
ground parts of the Palace, commenced to
joke about the columns or piers of béton which
supported the arches of the galleries, and, in
order to test their strength, took a short run
and gave one of them so violent a blow with
his shoulder that he knocked it all to pieces.
As, however, the galleries did not fall in con-
sequence, as they ought to have done, and
buried that gentleman and his suite, the story
somehow or other is not generally believed.
All the sixteen galleries reserved for ventilat-
ing purposes are prolonged about 60ft. clear
of the external wall of the building, and ter-
minate in walls, 10ft. in diameter, sunk in
the park. The galleries themselves are 10ft.
in width and 7ft. 3in. in height. Besides
these ventilating galleries, there are three
others of the same dimensions and one larger
one; the latter is nearly 33ft. wide and about
8ft. in height, and a great portion of it will
serve as offices and kitchens, and will be fitted
up accordingly.

weight of the iron. The qualities of the iron are not stated; but cobalt and nickel are known to give hardness to the metal, and the presence of them, even in the small amount above stated, may possibly confer some valuable properties.

In the manufacture of zinc a quantity of roughish grey powder is always obtained. It is often called grey oxide of zinc, but in general the greater part of it is the metal zine itself in a finely divided state. Dr. Stahlschmidt has found that this powder, which is easily freed from oxide and some impurities, may be applied to useful purposes by the chemist. Considerable difficulty, for example, has been found in manufacturing nitrite of potash. Stahlschmidt, however, finds that, by availing himself of the reducing action of this finely divided zinc, nitrate of potash is easily reduced to the state of nitrite, oxide of zinc, of course, being found, and also a little free potash. The author makes use of a saturated solution of the nitrate, to which he adds one-tenth its volume of ammonia and a quantity of the zinc powder. When this is heated to 30 deg. or 40 deg. Centigrade the action proceeds briskly, and it may be necessary to moderate it by the application of cold. In the course of half an hour the nitrate is so far reduced that the addition of twice its volume of alcohol to a sample of the solution causes no precipitate. The oxide of zinc is easily removed from the solution by means of carbonate of potash, which is then saturated with nitric acid, and the small amount of nitrate of potash is separated from the nitrite by crystallisation.

the present year, few will ever give a thought to the means whereby they are enabled to enjoy a constant supply of fresh and pure air. The subterranean galleries were constructed with the special end in view of providing in purity and abundance this indispensable requisite, and, in fact, principally for the purpose of ventilating the whole area of the exhibition, What may be termed the system of the natural ventilation of the building consists in the fresh air outside the Palace passing into the interior by virtue of the motion acquired by the well-known laws of density, while the vitiated air escapes through the louvres at the summit of the roofs. It is possible that this simple successive egress and ingress might be sufficient to effect a perfect ventilation, but it is by no means certain that the result would be of so favourable a nature. In an undertaking of the importance and vastness of the one under notice it would be fatal to its success to allow of the chance of such a serious contingency as imperfect ventilation to occur, more especially as it would be nearly impossible to remedy the evil of it, should it once arise. The Engineer-in-Chief, M. Krautz, has therefore proved himself worthy of the confidence placed in him, since As the subject of drainage is closely conhe has determined to provide against the nected with that of ventilation, particularly in possibility of such a mishap by reinforcing the this instance, where underground arrangenatural ventilation with artificial means. The ments have been made for both, we will say a system of forced ventilation adopted is known few words on the matter and describe the plan as that of M. de Mondésir, an engineer at-adopted for carrying off the surface water. tached to the service of les ponts et chaussées. The wrought-iron columns of the principal An expense of over a hundred pounds was gallery are hollow, and contain a zinc pipe to incurred in fixing up the machinery and receive the rain-water from the gutters and boilers in order to make a trial of the system conduct it to an earthenware pipe laid in the recommended by the engineer. M. Tresca, foundations, which is connected at the other Chemists know that freshly precipitated whose name is familiar to our readers, gave extremity with a drain running round the gelatinous silica is soluble to a slight extent his valuable assistance in observing and re- entire building. The cast-iron columns sup-in ammonia, but it has always been stated cording the results of the experiments. It porting the intermediate galleries act in a that ignited silica, or silica in a crystalline state, appears that the average volume of air drawn similar manner, and iron pipes are laid in the as quartz, is insoluble in ammonia. Wittstein, into the galleries per horse-power employed thickness of the side walls of those galleries however, has recently found that the latter was equal to 8,700 cube yards per hour, and which are not supported by columns, to take statement is untrue. He has found that both this quantity varied inversely as the velocity, the water from the gutters. All the smaller ignited and crystalline silica dissolve to a reaching to double the amount when the drains ultimately terminate in sixteen larger slight extent in ammonia. velocity was small. The volume also de- ones, which, in their turn, run into one cirpended in some degree upon the position of cular reservoir, 5ft. high, 2ft. broad, and 700ft. the traps or gratings. When the orifices of in circumference, which is in connection with ventilation were covered by them the air lost the main drain of the city, and finally finds its one-eighth of its volume, the motive power way to the Seine. The smaller drains vary and the amount of fuel used remaining con- with the volume of water they may have to stant. So far as the escape of the air is contain, from 1ft. to 1ft. 6in., and are all conconcerned the experiments were made under structed of béton, upon the plan of M. Coignet. very favourable circumstances, rather more favourable than what will be the case when the building is roofed in; but, making all allowance for this slight impediment, there is abundant proof that the air will escape with all the facility required.

The principal gallery, the refreshment gallery, and those appropriated to archæology and the fine arts will not be dependent upon the system of forced ventilation for their supply of fresh air, but all the others will have to drain upon that source should the natural ventilation fail to be sufficient for the purpose. The area to be supplied is about 90,000 square yards; but, bearing in mind that this space will be greatly reduced, respecting its capacity for containing visitors, by the amount of room occupied by the articles exhibited, it would be sufficiently accurate to regulate the supply for about 26,000 persons at a time. Allowing each individual 13 cubic yards of air per hour, it will be necessary to introduce into the building about 340,000 cubic yards, neglecting any quantity of air that may make its way through windows, passages, or by other means into these localities. In order to obtain this quantity eight of the radiating subterranean galleries are appropriated to the purpose, and it is calculated that each of them will afford a supply of over 40,000 cubic yards of air per hour. The engine will be of 5-horse power, and will consume in the same unit of time about

35lb. of fuel. The other eight radiating galleries will be devoted to natural or spontaneous ventilation, and will be separated from the former by partitions or brattices placed in the exterior circular gallery. Concerning

NOTES ON RECENT SCIENTIFIC DIS-
COVERIES AND THEIR PRACTICAL
APPLICATIONS.

Cobalt and Nickel in Irons-The Reducing
Action of Zine and the Manufacture of
Nitrite of Potash-Another Process for the
Valuation of Tanning Materials-Solubility
of Silica-Method of Preventing Boiler
Incrustations.

T"

HE results of the chemical examination of irons from various sources are of as much importance to the mechanic and the engineer as to the chemist. it is by comparing these with the physical qualities (hardness, tenacity, &c.) that the manufacturer learns how to produce iron possessing the requisite properties for different kinds of work. Looked at, in this light, the analyses of various irons recently published by Weiske have considerable in terest. This chemist has examined irons more especially for cobalt and nickel. These metals are present in English irons in very small quantity. Dr. Thompson, of Glasgow, who has made numerous analyses of Scotch, makes no mention of cobalt and nickel; and Professor Abel, of the Royal Arsenal, who made an elaborate examination of Nova Scotian and American irons, found in them only traces of cobalt. Weiske states, however, that, so far as he has examined them, he finds both cobalt and nickel universally present in irons, but in very varied proportions. He found the smallest amount in English pianoforte wire, but in some Saxony iron he found as much as 7 grammes of the two metals in a hundred

We gave two weeks ago an excellent process for estimating the amount of tannic acid in tanning materials. That process, though easy to a chemist and accurate, was perhaps beyond the skill of some who may wish to make such determination. We give to-day a readier method, which will perhaps be found as useful. It is by R. Pibram, who extracts one gramme of the material (oak-bark, valonia, divi-divi, &c.) by digestion with hot water, then filters the liquor, and precipitates with a solution of one gramme of sugar o lead in fifty grammes of water. The precipitate is collected on a weighed filter, then washed and dried. When it has dried, to a thin layer, the circular paper is to be doubled over, and the outer edge turned down, because the precipitate dries to a brittle, resinous mass, which is apt to split off, and pieces might be lost. The paper may now be perfectly dried at 120 deg. Centigrade and then weighed. The amount of lead is now determined by igniting in a porcelain crucible until no sign of carbon is left; then moistening the residue with a little nitric acid, drying, again igniting, and afterwards weighing. The difference between the weight of the dried precipitate and the residue of oxide of lead will give the amount of tannic acid. To arrive easily at reasonably approximate results, the author, applying the test under exactly similar conditions, allows the precipitate to deposit in graduated tubes, and guesses the amount of tannic acid from the volume of the precipitate. After a little practice we dare say this method might be usefully adopted, when strict accuracy is not required.

Friedrich, a German chemist, has published a method of preventing boiler incrustations, which, however, is only capable of limited application. He puts common pyroligneous acid into the boiler until the water faintly reddens litmus paper. This will, of course, convert the carbonate of lime into acetate, a much more soluble salt, but more of the acid must be added as often as the boiler is fed,

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since the excess will always distil off with theeeble to affect the nerve. And if several horses When the carbonate is the only lime were similarly included in one circuit, the same salt present in the water, this method will, no results were observed in each of them. The same doubt, prevent the deposition of crust, and the fact has been observed by M. Claude Bernardin common pyroligneous acid will probably be a prepared frog's limb in which the vitality of found as cheap to use as any boiler compo- duced current, convulsion occurs on closing the the nerve is unimpaired; with a sufficiently recircuit, and only then, whether the current be direct or inverse, because the terminal extra current is then inoperative.

sition.

THEORY OF

ON THE DYNAMIC
ELECTRICITY.*

in

BY C. BROOKE, M.A., F.R.S. NINCE I sent to you, through Professor Tyna short notice a tricity, I have had under revision my chapter on organic electricity, and have been forcibly impressed by the harmony existing between obvious deductions from the dynamical theory and some recently observed physiological results. The physiological effects of acting causes incidental to the transmission of a continuous voltaic current through a musculomotor nerve are of a complex character; they are universally acknowledged to be manifested only at the moments of closing and opening the circuit, but are modified by the influence of the current, during its prolonged continuous passage, on the portion of nerve-tissue included in the circuit. In order to interpret correctly all the observed physiological effects, it becomes necessary to consider carefully the dynamical consequences of the passage of a continuous succession of electric waves, here assumed to constitute a voltaic current; and it will appear that the physiological results are remarkably in ac cordance with the dynamical theory of electricity. The passage of a voltaic current, then, must comprise three distinct phases; first, the momentary passage of the molecules of the conductor from a state of rest to a state of motion; secondly, the indefinite continuance of molecular motion; and thirdly, the return of the moving molecules to a state of rest. The first phase will be accompanied by a rush or sudden impulse of increased potential in the direction of the current because there must be a condensation or accumulation of motion, in consequence of the inertia of the molecules at rest opposing the transmission of the wave; this may be termed the initial current. During the second phase there will be (supposing the potential of the current to remain constant for the time) continuous and uniform wave-motion. During the third phase, the excitation of motion ceasing, the vis viva of the moving particles will accumulate motion towards the termination of the conductor, whence a reflex motion may be expected to be propagated (as in the case of a wave travelling from the hand along a stretched cord, which reaching the fixed end, is reflected back again), giving rise to a momentary terminal current, inferior in intensity and opposite in direction to the initial current.

These initial and terminal currents (or impulses, as they might more appropriately be termed) have long since been recognised as the extra-currents of Faraday; but their relative direction and intensity have been assumed to coincide with those of the induced secondary currents, and therefore to be the reverse of what dynamical considerations have suggested; it has, however, been demonstrated by an experiment of M. Chau veau, that the dynamical view is the correct one. It has been proved by numerous experiments that physiological effects are produced, and produced only, by a sudden efflux of electricity from a nerve or muscle into a negative electrode, whether the active agent be a discharge of Frank. linic electricity, or either the induced or the extra currents, already mentioned. Starting from this as an admitted fact the experiments of M. Chauveau appeal to the most sensitive of all tests of the direction of an electric impulse (using that term as synonymous with "shock" or mentary current")-a living nerve. He places the electrodes of an electromotor over the opposite facial nerves of a horse, and having duly ad. justed the strength of the current, he finds that, on closing the circuit, that side of the face only is convulsed (by the initial extra current) the nerve of which lies under the negative electrode, and on opening the circuit the contrary side is less strongly convulsed (by the terminal extra current) the nerve of which lies under the positive electrode. M. Chauveau also found that with a still further reduced current, convulsion occurred in relation with the negative electrode only, the contrary or terminal extra current being then too Communicated by the author to the Philosophical Magazine.

mo.

even

The con

sure of from 20 to 22 tons to the square inch with the grain, and 18 tons to 20 tons against the grain-a degree of excellence which, under the trials with the apparatus in use at Chatham, the iron rejected has failed to attain. jected is superior to the standard laid down, and tractors, however, assert that the iron thus re refuse to submit to the dockyard tests, which, they contend, are not to be relied on, inasmuch as the testing apparatus is imperfect. In proof It may be bere remarked that the well-known of this they have placed in the hands of the Adrelative direction and intensity of the initial and miralty reports from two of the most eminent terminal secondary or induced currents in a se- iron testers, in which the samples of iron recondary coil are the necessary dynamical consejected by the dockyard officials were, on being extra currents. The initial extra current will ex- than the standard required by the Board. Pri cite a similar impulsive motion in the secondary vate and perfectly independent tests have likecoil, just as one stretched chord will excite an-wise been made, and again the results have been other capable of vibrating in unison with it (for adverse to the ruling of the Admiralty officials. electro-dynamic induction is probably quite ana- Under these circumstances the firm more partilogous to the reciprocation of sound); and the cularly concerned has intimated the intention of recoil of this impulse (the initial induced current) commencing legal proceedings against the Admi. will be weakened in opposing the continuous mo- ralty for the heavy loss they have sustained. tion induced by the continuous primary current. Again, the recoil of the impulse induced in the secondary coil by the terminal extra current in the primary (the terminal induced current), will likewise be in a direction contrary to that of the inducing impulse, but its potential will remain undiminished, as it is unopposed by any continuous induction; and it will therefore possess greater force than the initial induced current.

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THE "MIANTONOMOH."

HE visit of the United States' turretship

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following remarks in the Chronicle of the 15th Miantonomoh,' which arrived in this port yesult."The American iron-clad turretship But it may be asked by those who find diffi. terday, is the first vessel of her class that has culty in dispossessing their minds of long esta. visited Gibraltar, and is naturally the object of blished and time-honoured notions, is not all this much curiosity. The feeling that would be upperabout inertia and vis viva and impulses sheer hy most in most minds on first beholding this mon pothesis? Not so; the writer has long since ob- strum informe, ingens, of the waters would be served and recorded a precisely similar pheno-one of surprise that she could cross the Atlantic. menon (apparently an exact analogue of the in- Two huge turrets, the funnel, and the ship's tial extra current) in an unquestioned case of boats, suspended on their davits high in air, are wave-motion-an experiment on the interference nearly all that is seen above water. The ship of sound-waves, due in common with so many herself is a great platform rising little more others to the genius of Professor Wheatstone. above the surface of the sea than her own boats. Let the handle of a vibrating tuning-fork, held Molière's fencing master says that the whole art obliquely, rest on the surface of a table; as long of fence is comprised in two things-to hit your as it remains at rest, a loud resonance of the adversary and not to get hit yourself. The table is audible; but if the tuning-fork be moved 'Miantonomoh' seems constructed to carry out parallel to itself along the surface of the table in this doctrine in naval warfare. Her hitting apany direction, the resonance of the table imme- paratus, the two impenetrable towers with their diately ceases, from the perpetual interference Dahlgren 480-pounders, of which she carries two of the vibrations in successive parallel planes in each turret, is the only part she presents to an with each other. The instant the tuning-fork enemy, while the only part that he could hit to stops, the resonance bursts out again in a very do her an injury is wisely screened below the striking manner. If the tuning-fork be held ver- waves, except the narrow rim that, like the tically, the planes of vibration coincide, and the tower, is invulnerable. We have not heard what resonance is not interrupted by moving it. It can thickness of iron is beneath the platform deck scarcely be doubted that the impulsive recomthat supports the fighting part of the ship; but, mencement of the resonance, after its interrup- unless the deck is made as invulnerable to heavy tion by interference, is entirely due to the dyna. shot as are the sides and turrets, a vertical fire mical cause here assigned to the initial extrawould still find a weak point in these formidable current. M. Chauveau (no doubt correctly) as- ships. If ever Gibraltar should be attacked again cribes the physiological effect of an electric im- by floating batteries, they will be of harder and pulse to the dynamical molecular disturbance less inflammable material than those employed in which it produces. It will naturally be asked if the celebrated siege. General Elliot's red-hot electricity be only wave-motion, what is the na shot, instead of setting fire to the floating batture of that motion, and in what respects does it teries of the present day, would fly off from their differ from the wave-motion of light and heat? sides in a thousand glowing fragments, like the It is evident that the existence of two opposite sparks from heated iron beneath the blacksmith's electrical states must involve some kind of polarity hammer. If, then, heated shot are useless, and or directionality in the motion, not required to cold shot cannot penetrate the sides of modern explain the phenomena of light and heat. The ironclads, it would be a satisfaction, in case of atprobable dependence of magnetism on the circu- tack, if our artillery could penetrate them in lation of electricity round the molecules of the another way, by plunging shot upon their deck magnet would seem to suggest the idea of circu- from the level of the signal-house or the Rock gun. lar waves; and if these be supposed analogous To send shot through an attacking ship from top to the waves of circularly polarised light, the to bottom would be much more damaging to her phenomena of electric polarity may be rea- than sending it through from side to side. After dily explained. Moreover the state of mutualin- all, however, we cannot feel quite sure that our ductive constraint of the electricity of two op- ability to launch a vertical fire against an attackposed and oppositely electrified surfaces may being squadron will ever prove of practical advanroughly symbolised by the condition of two spiral springs, mutually compressing each other against an intervening obstacle.

DUR

GOVERNMENT AND IRON TESTING. URING the last few weeks considerable quantities of the plate iron sent into Chatham Dockyard by the contractors supplying that establishment have been rejected by the officials, on the ground of its alleged inferior quality and its failing to reach the standard of excellence insisted upon. The contractors have appealed to the Admiralty on the subject, and, after a long correspondence and numerous official reports, their Lordships have upheld the decision of their officers. The standard of excellence insisted upon by the Admiralty, and reported in the Times, is, that the plate iron shall stand a pres

tage. There is just now the keenest competition between the science of attack and that of defence. Who knows whether an enemy attacking Gibraltar from the sea on some future day may not have provided his vessels with im enetrable iron roofs, beneath which he may hammer away at our walls quite regardless of the shot that is pattering overhead like hail upon the slates."

At Ghent (Belgium) there is a Flemish newspaper published, the Gazette van Gend, which, perhaps the oldest in Europe, will have been in existence for the last two centuries on January 1, scribers are to receive a copy of the oldest number 1867. As a souvenir of this anniversary the subat present in existence. It bears the date of Sep. tember 8, 1667. The copies, which have been made by means of photography, have succeeded so well that it is difficult to distinguish the copy from the original.

ON THE INFLUENCE OF THE EARTH'S ROTATION ON THE DEVIATION OF PROJECTILES FROM RIFLED CAN. NON.*

BY M. MARTIN DE BRETTES.

THE HE distinguished geometrician Poisson treated this question in 1837 for the case of spherical projectiles, and has drawn the following conclusions: (1.) The ranges vary with the azimuths of the plane of firing, but between very narrow limits; for the greatest variation would be two decimetres for a range of 1,800 metres in firing from a mortar. It would be still less in firing point blank; so that, practically, the influence of the azimuth of the plane of fire on the ranges is zero. (2.) The influence of the rotation of the earth in our hemisphere causes a deviation of the projectiles to the right of the plane of firing, whatever be its azimuth. This deviation, whose magnitude is independent of the azimuth of the plane of firing, may attain a considerable value. Thus, from Poisson's calculations, a bomb of 32 centims. diameter at 4000 metres would deviate 8 metres in our latitude, owing to the rotation of the earth. (3.) The deviation increases with the latitude; it is greatest at the poles, and zero at the equator.

The influence of the earth's rotation on the aim of the fire-arms then used was very small relatively to that of the accidental causes which caused considerable variations in the direction and range from one spot to another. But these variations being now materially reduced in the firing of projectiles by rifled cannon, the influence of the rotation of the earth should be taken into account. This is what I shall show by compar

E, range..

D, lateral deflection † to the right

ing the deviation due to this motion with the total deviation given by experiment. As the calculation of the deviation due to the rotation of the earth at any latitude by Poisson's method is very tedious and therefore unpractical, I have used another, which is very expeditious and is virtually as exact as the preceding, as a comparison of the results obtained by each will show. This method consists simply:- (1.) In calculating the azimuthal angle e, described by the plane of firing about the vertical passing through the mouth of the piece, during the passage of the projectile. a This is performed by M. Foucault's formula,

0 = t w sin A,

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(1.) in which w is the velocity of rotation of the earth about its axis of figure, A the latitude of the place of experiment, both known quantities. (2.) In multiplying the range given by experiment by sin e. So that the deviation A due to the rotation of the earth is given by the formula,

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E sin (to sin λ)*. (a)

AE sin 0 = the following results for the firing of mortars of The formula of Poisson and this formula give 27 centims. at 1,200 metres, and of 32 centims. at 4000 metres, in our latitude :

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m.

m.

Mortars.

Deviation according to Poisson 1.20 formula (a) 1.27

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m.

m.

7:00 6.98

The agreement of these results confirms the
accuracy of the formula (a). Applying this lat-
ter to the firing of projectiles from rifled cannon,
we obtain, for the
FRENCH CANNON.

Projectiles of

ON THE CAUSE OF EXPLOSIONS IN LAMPS.

DU

BY JOHN ATTFIELD, PH.D., F.H.S. URING the last two months I have been in. vestigating the inflammable properties of mineral oils; at first, for the scientific interest the subject presented, then by desire of the Committee of the Petroleum Association of the City of London, and recently in elucidating the canse of an explosion of a lamp, at the house of gentleman in the country, Thomas Smith, Esq., the Croft, Sudbury. I am now, consequently, in a position to state the immediate cause of explosions in lamps, to show how it is that oils having dan. gerous properties occur in trade, and to point to more than one means whereby the use of mineral oils for illuminating purposes may be come as safe as that of the old, less valuable, vegetable oils.

The oil in a lamp passes up a wick by capillary attraction, comes in contact with the brasswork of the lamp in the long slit or channel which the wick by help of a strong current of air. The holds the wick, and finally burns at the top of flame heats the brasswork in its vicinity, the heat is conducted downward through the metal to the body of the lamp, and thence to the oil, which, after two or three hours, becomes considerably warmer than when the lamp was first lit. Now of 0.27. of 0.32. mineral oils, when sufficiently heated, emit vapours which form, with air, a dangerously ex. plosive mixture. The point to which any specimen of mineral oil must be heated before it yields this mixture can be ascertained readily and with perfect safety by the method proposed in my last paper "On the Igniting-point of Petroleum," namely, by half-filling an ordinary chemist's testtube, 6in. long and 1in. broad, warming, and well stirring with a naked thermometer until a small flame, frequently introduced into the upper part of the tube, occasions an explosive flash; the temperature indicated by the thermometer at this moment is the point of danger. Tested in this way, the oil from Sudbury afforded inflammable vapour at 83 deg. But, curiously enough, the temperature of the bulk of the oil in the lamp that exploded, never reached this point; for, besides the greater part of the two gallons of oil, a portion of which was in the lamp at the time of explosion, the brasswork and fragments of the lamp had been forwarded to me, and I was thus enabled, after fitting on another glass body, to experiment on what might be considered

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, angle of firing

17 deg.

3200m.

14 deg. 1400m.

45 deg.

2800m.

t, time of flight

178.

12s.

30s.

198m.

A, deviation due to the rotation of the earth..

2m,90

46m. 1m.67 4m.50

310m.

318. 494m. 5m.80

A

1

1

1

1

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The smallness of the deviation due to the deflection, shows that this is practically negligi. as the original lamp and original oil, and found earth's rotation, as compared with the total ble.

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Thus the effect of the earth's rotation contri- | would change its sign in the opposite hemisphere, butes half the total deflection of the projectile; hence this influence cannot be neglected. This deviating effect of the terrestrial rotation may give applications useful in ballistics. Thus :- (1.) When in our hemisphere the effect of the earth's rotation amounts to half the deviation of a projectile to the right of the plane of firing, if the direction of the rifling of the cannon be changed, the deviating action of the air changes also; the effects of rotation and of the resistance of the air destroy each other; so that the projectile will fall in the actual direction of the line of firing, and the deflection will be almost zero. (2.) On passing from one hemisphere to the other, the direction of the rotation changes, and quently that of the deviating action on the projectile.

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part of the body of the lamp was not warmer than 65 deg, a mixture of vapour and air had formed in the upper part of the body and exploded on a flame being introduced. Here, then, was a sample of oil, a portion of which had been the source of an explosion under ordinary domestic circumstances, which emitted no infam. side the lamp, and yet which inside the lamp mable vapour under 83 deg., when tried out. gave, at 60 deg. to 70 deg., such a mixture of vapour and air that, should it catch fire, would inevitably explode. The explanation of this state of things was obvious. The oil, though at 75, 65, or even colder, had, in its passage up the wick to pass through the heated brasswork, the temperature of the gateway of which, the tem perature of that part presented to the interior of the lamp, must have been high enough to cause the evolution of vapour into the air in the upper part of the interior. This temperature was taken by appropriate means and found to be 108 deg.; in a smaller lamp it was 105 deg., and in other experiments varied from 100 deg. to 110 deg. during an evening. The cause of the explosion was thus perfectly clear. An oil giving inflam mable vapour at 83 deg., and not apparently heated beyond 60 deg. to 70 deg., had actually been exposed, in a most complete manner, to a tempera. ture of 108 deg., resulting in the formation ignited on turning down the wick. Every person of an explosive mixture, which accidentally who had used this oil in a paraffin lamp of the usual form had, so to speak, been burning his candle over a charge of gunpowder, and were it not that the chances of the explosive mixture becoming ignited were exceedingly small, as will

be presently shown, many explosions, before that now recorded, must have attended the use of the oil. So, then, an oil giving inflammable vapour below 110 deg., and burnt in a lamp of ordinary construction, yields, sooner or later, a gaseous mixture, which, should it catch fire, will burst the lamp and scatter the oil, to the possible in jury of property and danger to life. Practically, I have only obtained lamp-explosions with oils which give off vapour below 100 deg., when examined in the test-tube in the manner above described. Unfortunately, fourteen out of every fifteen specimens of "crystal oil," "photogen," "American paraffin oil," and other varieties of petroleum now sold for illuminating purposes, generate the explosive mixture at temperatures much below 100 deg., and hence are dan. gerous. The same remark does not apply to Young's paraffin oil, but there is reason to fear that this mineral oil is often diluted with dangerous American oils. Other home-made mineral oils also vary in explosibility.

The explanation of the occurrence of dangerous mineral oil in trade was fully traced out in my last paper; three sentences, therefore, will be sufficient on this head. Crude petroleum having been found to be inflammable at common temperatures, an act was passed in 1862, for. bidding, except by licence, the storing of petroleum and its products near a dwelling-house or warehouse in larger quantities than forty gallons, unless proof was forthcoming that it gave off no inflammable vapour at a temperature of less than 100 deg. of Fahrenheit's thermometer." Unfortunately this was taken to mean, and probably did mean, that the petroleum itself should not ignite under 100 deg. when heated by a flame or a water-bath in an open saucer or small bowl-a most fallacious test, first, because the time employed in the operation, the amount of stirring practised, the form of the vessel, its arrangement over the source of heat, the quantity of liquid used, and the distance of the test-flame from the surface of the petroleum, all influenced the result to the extent of causing two observations to vary from 4 deg. to 40 deg. from each other; and, second, because the experiment thus performed invariably gave the igniting point many degrees higher than the temperature at which inflammable vapour was evolved than the temperature, therefore, at which the oil was dangerous. Shippers, merchants, brokers, adopted this fallacious mode of testing; oil changed ownership under a warrant that it would not ignite under 100 deg., not, however, without occasional litigation caused by the uncertainty of the test, and hence the market was and is supplied with oil which emits inflammable vapour in most cases below 90 deg. and often below 80 deg.

favour of an accident, even though an explosive 1789, adopted 3 hours 2 min. 35 sec. for the lon-
mixture be constantly in the reservoir. Were gitude of Rio Janeiro at the point called Ville-
this not so, explosions with petroleum now in gagnon, contenting himself with a voyage across
commerce would be the rule rather than excep- the Atlantic, made with a single chronometer;
tion. Blowing down the chimney of a lamp while Triesnecker's data would have 3 hours 1
neutralises this current, and doubtless increases min. 57 sec. In 1842, Daussy published a note
the chances of the flame reaching what I have in the Connaissance des Temps, in which he
already termed the touch-hole. Then this fixed the longitude of Rio exactly at 3 hours 2
channel of communication might be packed min. M. Mouchez, having for some time past
with wires after the principle of the oxy-hydro- been engaged in a complete survey of the coast
gen safety.jet. Again, the portion of the brass-lying between the River Plate and the Amazon,
work facing the interior of the lamp should be found it, of course, necessary to determine anew
covered with bone, glass, or some other material, this disputed longitude of Rio, and, after five
having bad conducting powers for heat, so that years' observation, has come to the conclusion
the gateway, as I have before called it, through that Triesnecker's longitude, derived from the
which all the oil has to pass in ascending from the transit of Mercury, is minutely exact. He was
reservoir to the flame, shall be cool instead of about to adopt it for his chart, when, to his sar-
hot. By these means, and especially by de-prise, he found another longitude marked in the
manding that all mineral oils shall comply with Connaissance des Temps for 1867. This longi-
the letter instead of what is said to be the spirit tude has been determined by M. Liais, who
of the Petroleum Act of 1862, explosions in affirms that he has calculated his observations
lamps will seldom or never be heard of.
with the greatest care, and repeatedly verified
the result. And yet there is between this and
Triesnecker's a difference of thirty seconds,
which is so enormous that it could never have
escaped detection by any captain having three or
four chronometers on board; nor is there at pre-
sent any single maritime point on the globe sub-
ject to doubt to such an extent. M. Mouchez is
decidedly of opinion that the longitude adopted
by the Connaissance des Temps is wrong; and as
that work is in the hands of most mariuers we
have considered it our duty to notice the oir-
oumstances.

THE

A few words in conclusion. I have pointed out the cause and the remedy; with whom will begin the adoption of the means of prevention of these explosions? It is useless to say the refiner ought to do this; the refiner at New York and Philadelphia satisfies the requirements of the shipper; the shipper sends whatever is wanted by the British merchant; the merchant imports accord. ing to the demands of the dealer; the dealer supplies the warts of the retailer; and the retailer finds ready sale for any mineral oil that will give a good light without smoke, and is cheap. Then the adoption of preventive measures scarcely lies with the public; for the consumer seldom knows MANCHESTER BOILER ASSOCIATION. anything about thermometers, petroleometers, HE last ordinary monthly meeting of the igniting-points and exploding-points, and the executive committee of this association was only test I can suggest to him, by which to assure held at the offices, 41, Corporation-street, Manhimself that a given specimen of oil is or is not chester, on Tuesday, November 27th, 1966, dangerous, is to unscrew the brasswork after the Hugh Mason, Esq., of Ashton-under-Lyne, Vicelamp has been burning for an hour or two, and President, in the chair, when Mr. L. E. Fletcher, to introduce the flame of a lucifer or thin splint chief engineer, presented his report, of which of wood into the reservoir of the lamp. A light the following is an abstract:-During the last blue flash of flame, visible within the aperture, month 342 engines have been examined and 503 and scarcely audible explosion will result if the boilers, as well as three of the latter tested by mixture of air and vapour in the upper part of hydraulic pressure. Of the boiler examinations, the reservoir is inflammable. Such an experi. 408 have been external, 9 internal, and 86 entire. ment is as harmless as that of lighting raisins In the boilers examined 77 defects have been dissoaked in brandy in the game of Christmas snap-covered, 10 of those being dangerous. The foldragons. If the explosive mixture is met with, lowing is a statement of defects, omissions, &c., the oil is dangerous, as the ignition of the mixture met with in the boilers examined from October may occur when the aperture is closed by the 27, to November 23, 1866, inclusive. Furnaces brasswork; in that case the resulting flame and out of shape, 1; fracture, 6 (1 dangerous); lisexpanded products of combustion, having no tered plates, 3; internal corrosion, 2; external other vent, will escape by bursting the reservoir, corrosion, 9 (4 dangerous); water gauges out of and scattering the oil, to the risk of a conflagration order, 15; blow-out apparatus out of order 8 if the oil catches light. If there is no explosive (2 dangerous); safety valves out of order, 3; mixture in the reservoir the oil is safe, and will pressure gauges out of order, 4 (1 dangerous); even extinguish the test-flame if the latter boilers without safety valves, 1; boilers without The remedy is plain. Let those who sell and is plunged beneath the surface. Experiments of blow-out apparatus, 2; boilers without feed backthose who buy discountenance the sale and use this sort would, of course, result in a demand, pressure valves, 20; cases of deficiency of water, of those qualities of mineral oil which generate which, passing on from mouth to mouth, would 3 (1 dangerous). The case of fracture above inflammable vapour at temperatures below 100 at last produce a supply of safe oil from the refiner. alluded to is, perhaps, one more pregnant with (better 110) deg., when examined in a test-tube But we must not expect such tests to be performed danger than any before met with in the inspeoin the mauner already indicated. Such tubes to a commensurate extent by the public. We tions of this association. It was found in one of may be purchased for a few pence of any must turn to the trade in this matter, and look three boilers, all of which were about 7 ft. 6in. in chemical apparatus maker, naked thermometers to them to adopt this experiment, in its, to them, diameter, connected together, and worked at can be obtained at the same places, or these easier form of the test-tube and thermometer a pressure of nearly 60lb. on the square inch. articles, together with an instrument for ascer- already described, and to regard no refined oil The defect consisted of a crack, which ran from taining the power of the oil to ascend a wick, as merchantable if it gives off inflammable vapour, rivet hole to rivet hole of the inner overlap a spirit lamp, test-flame jet, directions for use, or, in other words, if it affords an explosive mix of the plate, at a longitudinal seam of rivets &c., all enclosed in a neat pocket case under the ture below 100 deg. Fah. But with which near to the top of the boiler, the depth of the name of the petroleometer, are now kept in stock of the above-named classes trade crack being half the thickness of the plate, by Mr. Casella, Hatton Garden, London. Oils will this reform begin? Who will find it to his while it extended to within a few inches of its which stand this test may be considered safe, interest to discard his old standard of 100 deg. entire width. Had it developed, as many cracks and such oils can be supplied by refiners as easily as the temperature below which the oil itself do, as unsafe ones—it is only a matter of carrying the refining operation a little further. Indeed, safe oils are even now occasionally met with. At a shop in Drury-lane I purchased petroleum at 4d. and at 41d. per pint; the former yielded inflammable vapour at 86 deg., and gave me an explosion the first hour it was burnt in a lamp; the latter only emitted vapour at 114 deg., and gave no explosive mixture in a lamp, even after seven hours' burning. The use of safe oils will be the chief means of avoiding explosions. But the lamps themselves are not altogether faultless. The air-hole which allows of air entering the lamp and taking the place of escaping oil is usually within about half an inch of the flame; it might very well be placed at some other part of the lamp, for it is this aperture which forms the touch-hole by which fire is conveyed from the flame to the explosive mixture within. Fortunately there is always a strong draught of air in the opposite direction, so that the chances are perhaps five hundred against to one in

of the

shall not ignite, and adopt instead the higher
standard just given? Perhaps the Committee of
the Petroleum Association will bring about this
reform, and thus ensure safety to the public. If
the trade will not help the consumer, possibly
the excise, the press, or Parliament will take the
matter up. If neither comes to the rescue, we
must put up with an occasional explosion and its
attendant fright, fire, or loss of life, or else leave
off burning these valuable oils altogether.

So as to lead to the rupture of the plate, the most serious consequences must have resulted. Not only would the shell of the boiler in question have been torn to pieces, but the adjoining boilers thrown from their seat, and possibly exploded from the shock, as has been found

to be the case under similar circumstances. The boiler was but about three years old, so that it shows that "entire" examinations are im. portant even for new boilers.

The following is a statement of explosions from October 27 to November 23, 1866, inclusive:No. 50 (November 1), double-flued marine, internally-fired, 5 persons killed; No. 51 type,

LONGITUDE OF RIO JANEIRO. Na paper addressed to the Academy of M. adverts discrepancy existing with regard to the longitude of ternally-fired, no one killed or injured; No. 52 the capital of Brazil, and which may be of consider- (November 5), particulars not yet fully ascerable importance to navigators. Until now there tained, no one killed or injured; No. 53 (Novemhad been an uncertainty varying between five ber 11), single flue or Cornish, internally-fired, 1 and ten seconds in this longitude. Admiral person killed and 1 person injured; No. 54 (NoRoussid, without taking into account Tries-vember 20), plain cylindrical, for steaming rags, necker's determination of the meridian of Monte no fire, no one killed or injured. Total, 6 persons Video by means of the transit of Mercury in killed and 1 person injured.

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