spindles. The process adopted by the author Such a vessel, he contended, could be constructed was ventilated by means of a copper fan, of large for the detection of sulphur is very simple. on a displacement but little different from that of diameter, suspended horizontally under the deck, He merely digested the oil for some hours at a the "Bellerophon," and it would not only be im- and driven by a small donkey-engine, bolted to gentle heat with a small piece of potassium. penetrable now, but would probably remain so the deck beams. The fan, which was not enThe metal became coated with a reddish crust, for some years. He considered it had been shown, closed in a casing, drew the air, which it sent and there was a slight evolution of hydrogen. by ample experience, that such vessels were sea- into the engine-room, through a pipe or cylin After the digestion water was added, and the worthy, afforded comfortable accommodation for drical trunk, 4ft. in diameter and 8in. thick, the crew, were healthful, and popular with sailors. carried high above the deck. The air thus aqueous solution was tested with nitro-prusside In the common ironclad, as the armour had to forced into the engine-room passed thence into of sodium. The result was a deep purple- be spread over a high side, it was necessarily the boiler-room, to maintain the combustion in coloured solution, which showed the presence thin and weak; whereas in the monitor system, the furnaces, which was also aided by two of a considerable amount of sulphur. On dis- the sides being very low, the area to be protected Dimpfel blowers, each 78in. diameter, applied tilling the oil, the author also obtained sul-was reduced to a minimum, so that with the same under the turret, through the top of which the phurous acid. Dr. Vohl is of opinion that displacement the armour might be made of great air was drawn. The sides of the ship were only when the raw oil is treated with concentrated thickness, such as would be impenetrable by the 16in: above the water line, and were defended sulphuric acid in the refining process, some heaviest existing ordnance. The "Kalamazoo" by armour 6ft. deep and 4ft. thick, 104in. of sulphur compounds are formed which are not class of monitors had side armour 14in. thick this thickness being of iron, and the remainder backed by several feet of oak, and these vessels of oak. The turret was of iron, 24ft. inside removed by the subsequent treatment with an alkali at the ordinary temperature. Paraffin Possessed great facility of evolution, as they diameter, 9ft. 6in, high, and 15in, thick. The were fitted with balanced rudders and twin screws. vessel tapered to a point at each end, the side oils are sometimes bleached by treatment with In both the armour and the guns, the broadside armour being continued so as to form a ram both chlorine and chlorine compounds; and, as system was one of diffusion, the turret or monitor at the stem and at the stern; and by this projec the presence of these in a lubricator would system one of concentration. The former had tion at the stern both the screw and the rudder also be objectionable, Dr. Vohl examined the been adopted in France and in England, the latter were effectually protected. The weight of each oils for them, but obtained only a trace of chlo- in America, where about sixty vessels of this class shot discharged by the 15-inch gun was 425lb. rine in one. Hydrofluoric acid also bleaches had already been built, and recently by Russia and and the quantity of powder burnt every charge parafin oil, and greatly modifies the odour of some other continental powers. In the broadside was 60lb. ita We have never heard of the practical system the only material innovation on the model Comparing the destructive and resisting powers use of this agent, but Dr. Vohl states that he of the old men-of-war was in the application of of such a vessel as the "Dictator" with an iron. has found it in a lubricating and also in a burn-iron armour to the sides. In some cases the clad like the "Bellerophon," the latter carrying armour was not extended to the bow and the on each broadside five guns of 10in. bore, ing oil. In the former it is highly objection- stern, but only the central part of the sides and besides two guns at the bow and three at the able, since the oil quickly attacks metals; and a belt at the water line were protected, and stern of 7in. bore, it was contended that none of in the latter it is no less so, for in the combus-armour bulkheads were carried across the ship, these guns could pierce the iron turret, or low tion it gives rise to the formation of a highly before and behind the protected portions of the sides of the former, or the deck, composed as it irritating vapour, which causes inflammation sides, so as to form the central part of the vessel was of oak planks, 9in, thick, covered with 2in. of the eyes, destroys colours, and acts on into a rectangular fort. This was the principal of iron, and that all the parts of the vessel were glass. on which the "Bellerophon" and other recent equally strong to resist the forces that might be vessels had been built, and its advantage was brought to bear against them. It might be that it enabled thicker armour to be applied. In supposed that the Dictator" would be easily the monitor system, the guns, which were of run down by the "Bellerophon," but this was large calibre, were carried in one or two cylin- argued to be impossible, even if the former were drical towers of iron, and the weight of the broad-stationary, nor did it agree with experience, for side was concentrated in one or two enormous the "Merrimac," when she encountered the first shot, which had momentum enough to go through the armour of any of the broadside vessels of the Royal Navy of Great Britain. Dorlac and Samimi, in a paper on the manufacture of lime in the Department of Mayenne, assert that chalk parts with its carbonic acid more easily in a current of steam. They state, in fact, that 100 parts of chalk lost in steam 3.1 parts more carbonic acid than in air, and thus produced a stronger lime. Another assertion of the authors is, that chalk increases onetenth in volume when burnt into lime. It is generally stated that a decrease of volume takes place, but the authors seem to have made their experiments very carefully. There were certain points of dissimilarity between the turret ships of Captain Coles and those of Captain Ericsson, the most material being that the sides were not nearly so low in the former as Dr. Jacobsen gives a very ready test for the in the monitors, and the armour of the sides and detection of rancidity in oils. Dry rosaniline displacement. be made so hick; nor would it be the turrets could not consequently, with any given is completely insoluble in neutral fats; but if possible, wi h safety to reduce the height of the the smallest proportion of a tatty acid is pre-sides, owing to the turrets being carried on rollers sent, the rosaniline dissolves, giving a colour on the lower deck, thus passing through openings in proportion to the amount of the acid present. in the upper deck, which it was difficult to keep The test may also be useful in the examina- tight without jambing the turrets; the openings tion of animal and vegetable oils intended for to the engine-room were also merely covered use as lubricators. with gratings, or were otherwise similarly unprotected. In the monitors, on the contrary, the deck, and all the openings to the interior of the turrets revolved upon a metal ring, on the upper vessel were through the top of the turret, or through shot-proof trunks or pipes, so that even if the deck were washed by the waves, water could not enter the vessel so long as the deck remained watertight. Captain Coles's vessels had been but little tested in actual war, and therefore the objections urged against his system had yet to be proved. On the other hand the monit rs had been found, during a war of unprec magnitude, to be both shotworthy and seaworthy; they were confessedly unequalled in their power of penetrating other vessels and of resisting penetration themselves. Dr. Wiederhold gives a receipt for a glazing free from lead, and adapted for ordinary pottery, and especially for cooking utensils. It is a mixture of silicate of soda or potash and borate of lime-the ordinary boro-calcite from South America answers. The two have only to be mixed together so as to form a thin paste, and can then be used in the ordinary way. The inventor, we are bound to say, speaks doubtfully of the value of the glaze, but the process deserves a trial. INSTITUTION OF CIVIL ENGINEERS. structure monitor As an illustration of the main features of the monitor and tried to run over her, suffered far The main point connected with the structure of the monitors, which had provoked controversy among naval men, was whether it was possible to make heavy vessels, so low in the water a the monitors were, safe at sea. Even if this should be doubted, the necessity for the employ. ment of monitors for the protection of ports, harbours, and estuaries, was not the less exigent, seaworthiness and height of side were indissolubly But although, in the nautical mind, the ideas of associated, it was believed that it would not be difficult to show that there was no necessary connection between these conditions. In the monitors, the deck was as tight as the bottom, and the only openings to the interior were through towers which the waves could not enter. Moreover, such vessels did rise to the sea, and it was found in practice, that towers of the deight of those of the "Dictator" were quite Gregory, Esq., vice-president, in the chair, the was given of the American war-steamer "Dic- all. The heating surface of the boilers was equate to enable the vessel to encounter with safety the heaviest seas to which any vessel could be subjected. During the two years the monitors were exposed, on a stormy coast, to all kinds of weather, they proved to be both shotworthy and seaworthy, and the healthiest vessels. of the "Monadnock" round Cape Horn, and of the "Miantonomoh" across the Atlantic, had caused the most plausible of the objections to the system to be abandoned. Various other objections were noticed, as, for instance, the want of liveliness imputed to the monitors, but this it was argued was a material advantage in any vessel requiring to take an aim with heavy guns, since it must make the aim more sure. In conclusion, the author said, what it concerned the Government and the country to know was, that in the Royal Navy there were vessels of at least equal powers in guns and in armour to those possessed by any other nation, so that in the event of a naval war, the broadside fleet might not be disabled or captured, from the want of a flotilla of protecting monitors, whose function it would be to encounter any similar vessels belonging to the enemy. A SELF-EXTINGUISHING SAFETY.LAMP. FEELING has long existed that many lamentable explosions in collieries would be prevented by the exclusive use of a safety-lamp which, whilst affording an abundance of light, should remain securely closed so long as the flame is unextinguished. To obtain an abundance of light, no lamps are equal to those of the Clanny or Mueseler pattern, but in this country there has usually been a great objection to it, owing to the existence of a fear that the glass would get damaged, and deprive the lamp of its advantages, notwithstanding the fact that scarcely one, if any, instance is known of an explosion caused through the failure of a glass in the whole of Belgium, although the Mueseler lamp has been almost exclusively used there for many years. The recent calamities having caused fresh attention to be directed to the prevention of explosions, the subjoined description of an ingenious self-extinguishing safety. lamp will be generally interest For a similar reason the liquid particles adjacent to As the consecutive portions of ice are formed ing. The object of the invention, which, says the solid state, this transition takes place at a tem- apparent. Before proceeding to the consideration of the problem itself I shall establish the following theorem:-If A denote the latent heat of water at the temperature 32 deg.-t, deg., A the latent heat of water at 32 deg. and c the mean specific heat of ice at the temperature 32 deg.- t, then To prove this, consider one pound weight of water at the temperature 32 deg. t, deg., and sup. pose it (1) converted into ice at the same tempe rature, then (2) raised as ice in temperature to 32 deg., then (3) converted into water at 32 deg., and finally (4) cooled down again as water to 32 deg. — t1 deg., and consequently brought back to its original state. Now since ON THE FREEZING OF WATER AT LOW the quantity of heat latent and sensible in the TEMPERATURES.* BY ARTHUR HILL CURTIS, LL.D. WHEN water which has been reduced in temperature below the ordinary freezing point without becoming solidified is agitated, it is well known that a portion of it becomes frozen; and the question immediately arises, how much? This question has been already answered, and the result arrived at tested by experiment. In obtaining the result, however, it has been assumed that all the ice is formed either at the temperature of 32 deg. Fah., or at the initial temperature of the water. Now a little consideration will show that neither of these assumptions is true. The congelation commences at some one point, or at a certain finite number of points; certain small particles of ice are formed at these certres of congelation, a large quantity of heat is given out by each particle, and as water is a bad conductor of heat, this is principally communicated to the adjacent particles of water, and when immediately after wards these particles pass from the liquid to the Communicated by the author to the Philosophical Magazine. pound of water is the same at the commencement (1) and (e)) met be in the stages (2) of 103). &c., while W- (91 + 9a +93 + &c.), is heated as or The quantity which is here denoted by λ is the 0 79.25' of the water in its initial state, as determined by BOILER EXPLOSIONS NOT ALWAYS T quency, the readers of our public journals intervals, recurring with terrible freare startled and shocked-if familiarity has not indeed bred callousness-by accounts of steam boiler explosions, attended always with loss of property, and often with loss of life or limb. To no other subject is the old adage, "in too much discussion the truth is lost," more applicable than to that of boiler explosions. The cause of these catastrophes has been so muddled by wordy dissertations, mysterious theories, and senseless conjectures that few think of looking directly at the facts of each individual case and deciding each on its own evidence. Mysterious agencies, ander the names of contraction," "expansion," "electricity," "development of explosive gases," and others, figure conspi. cuously in the reports of committees of inquiry. The causes which are most obvious, or could be most easily ascertained, are overlooked, and the investigators go prowling about among unknown or not understood forces, to find that which fre quently is before their eyes. Braces originally too weak, corroded, or improperly located; plates running longitudinally instead of circum. ferentially; defective riveting; plates weakened 66 by large holes not filled with thpor iron, ciency in the thickness of plate; poor iron, and carelessness in calking, are overlooked, to say firing, or neglected water feed, and incompetent nothing of corrosion from impure water, hard attendants. Sometimes, in riveting, the holes in the plates diverge half their diameter, and they are reamed to a circular form, or enough to admit the ordinary rivet, which cannot fill the space, and depends for its security wholly on the juxta position of the heads with the surface of the plates. Heat expands the iron, loosening the rivets, the water works through, and, if containing salts, oxidises the iron, opening the way for a rupture. The careless use of the calking chisel sometimes cuts into the plate or of its thickness, so that when an explosion occurs the line of the fracture follows the channel thus made, as the breaking of glass follows the dia. mond scratch. λ1+t1 =λ+c1 t1, or λ1 = λ — (1 — c1) t1. (1) It may be remarked that no assumption is here made about the specific heat of ice being constant for different temperatures; c, t, is, in fact, only a symbol for the entire quantity of heat necessary to raise one pound weight of ice from 32 deg. t, deg. to 32 deg. This being established, I shall now proceed to consider the question proposed. Let W denote the weight in pounds of the given quantity of water inclusive of the containing vessel reduced, 32 deg.—t deg. its temperature, and Q the weight of the ice formed; let q, denote the weight of any particle of ice, ti the temperature at which it was formed, A, A, C being as above; let qa, ta, Aa, ca be similarly related to a second particle, q3, t3, A3, c3, to a third, and so on; then, as qi, q2, &c., are respectively heated as water through t deg. ta deg., &c., and as ice through t, deg., tz deg., only a few months ago, by which a number of t1 deg., t deg. persons lost their lives. An investigation was had before the coroner's jury, which resulted in a perfect mystification. Yet the cause or causes should have been apparent in several facts which were ascertained. First, that part of the boiler that gave way was so deficient in substance, that, at the maximum working pressure, the iron was strained to nearly its rupturing limit; the factor of safety, instead of being 5 or 6, being hardly above 0. Second, the sheets, instead of being placed circumferentially so that the joints would not be so long in the direction of the length of the cylinder, and so that each would support the adjacent ones, were placed with the long diameter running lengthwise. Third, the calking iron had injured the iron along the seams nearly 20 per cent., and the braces were placed in an improper manner. It can scarcely be contended that this was an exceptional case. It is to be feared that many of our boilers would not stand a thorough scrutiny on these points. Mr. Edward B. Martin, an eminent engineer of Stourbridge, England, recently read before the Institution of Mechanical Engineers a paper which exhibited the following facts:-During the present century there have been 1,045 boiler explosions in England, causing the death of 4,076 persons and injuries to 2,903. Of the 1,045 explosions, 397 were "uncertain" as to cause; 137 were from over-pressure, from the wedging or over-weighting of safety valves, or from other facts of carelessness; 119 from collapse of internal flues; 114 from shortness of water, or from incrustations, and 9 from extraneous causes not immediately connected with the boiler. From these facts Mr. Martin expressed himself as opposed to all ideas of internal detonation, spontaneous generation of explosive gases, or other mysteries. If this is approximately a correct exhibit of the causes of boiler explosions in England, need we look for some mysterious and unknown agency to account for similar occurrences here? It is well known that English mechanics and engineers are held to strict accountability by the laws, much more so than in this country. It may be claimed that the tenacity of American boiler plate is superior, and such extreme caution as is enforced in England is unnecessary here; AGRICULTURAL CONDITION OF FRANCE. As a test of this quality it may be stated that this light can be seen through the flame of coal gas as a white image on a yellow ground; and, as proof-light constancy, the inventor has had a lamp a-light for two weeks night and day, a duration impossible to be attained with lamps of any other kind. THE Government commission of inquiry into THE PYROGENIC OIL GAS LIGHT. our readers. THE USE OF STEEL FOR BRIDGES THE but in this matter as in others it is "better to be his principle to the lighting of ships, railway Board of Trade have issued circulars and foolishly careful than foolishly careless." We believe that a rigid examination of boilers and a thorough oversight and testing during the process of manufacture, as well as after completion, enforced by legislative penalties, would prevent some, at least, of the destructive explosions which we are too often called upon to deplore. -Scientific American. THE EIDOSCOPE. carriages, &o.; and in 1864 he patented further have obtained several replies as to the probable effect of the use of steel in the construction of bridges and ships. The replies generally are favourable to its use, but it is not recommended that the weight of steel employed should be so much reduced as would be due to the proportion in which its tensile strength exceeds that of iron. It is also recommended that further experiments should be made. A certain thickness is no doubt felt to be required to provide for wear and the action of the weather, over that which might be theoretically necessary to withstand the strains THE eidoscope is among the most recent novel- and liable at any moment to explode is a danger to which the structures may be subjected. The ties at the Polytechnic Institution, having been introduced there at the last Christmas session by Professor Pepper, to whom, we believe, the contrivance was first suggested by Professor Wheatstone. This ingenious invention can be made a most valuable accessory to the magic lantern, and it is matter of much surprise that such novel and beautiful effects should be obtained by means of a mechanical contrivance of such extreme simplicity. Unlike the kaleidoscope, invented by Sir David Brewster, in 1814, in which symmetrical effects were evolved by reflection from a number of irregularly shaped objects the eidoscope produces geometrical figures of exquisite beauty by a simple revolution of two perforated metal discs on their own axes. As the discs are slowly revolved, new and infinitely varied forms are created, together with the most delicate gradations of tone. It is a remarkable feature that while these changes are in progress, one perforation, and one only, on the upper plate, will be found perfectly coincident with another on the lower, while all the rest are irregular and form different combinations. When, however, for the magic lantern the discs are put into more rapid motion the greatly accelerated velocity, instead of producing geometrical figures, flashing rays of light appear and are projected on the screen with the most extraordinary results. By employing variously coloured dises of glass or other material in connection with the eidoscope the most gorgeous effects of colour may be obtained. Board of Trade have laid it down as a rule that ous nuisance. How he proposes to remove this the material of a structure, whether this material catalogue of deficiencies will be seen by a be of iron or steel, shall not be subjected to description of his lamp and oil. In all cases a greater strain than five tons per square inch. As reservoir of glass or metal contains the oil; a it is well known, says the Scientific Review, that wide tube closed at the bottom descends nearly steel will bear a much greater tensile strain than to the bottom of the reservoir and displaces a iron, this rule of the Board of Trade operates central column of the oil. Into and through the as a great restriction on the use of steel in bottom of this closed tube is fixed the burner, bridges, &c. The experiments which we at prewhich is a tube of smaller diameter, containing sent possess on the strength of steel are neither a cotton conductor, whereby the oil is raised to sufficiently numerous nor authoritative to fix defi. near the top of the burner. Above this is a gas nitely the number of tons per square inch which chamber, which is perforated with a double row will express as a rule the strains to which steel of holes for the escape of the gas to burn. Now may safely be subjected. It is therefore very de. the heat generated in burning is, by the conduc- sirable that trustworthy experiments on this subtion of the burner tube, constantly carried down-ject should be made, and continued from time to ward, but the current of fresh cold oil constantly rising upward intercepts the descending heat and employs it in its own vaporisation. Thus the whole of the heat generated is used for intensify ing the light, and none of it is allowed to communicate by conduction to the general bulk of oil in the reservoir a condition of twofold advantage, ensuring conservation of heat to increase the quantity of gas, and preservation of a low temperature to the bulk of the oil below, by the perfect detachment of the burner, throughout its whole length, from all connection with the reservoir containing it. The burner, thus increased in vapour-generating power by its isolation and differential action, provides for combustion at the highest possible temperature by projecting horizontally into the air its in gas from two tiers of jets, arranged one above another, each jet falling in the interstice between two jets in the next row, and their The damage done to Plymouth breakwater by the proximity is such as to allow the best proportion late gales is estimated at £40,000. of air between each for producing a white light. flamed time, as improvements are made in the manu facture of steel. Above all, uniformity in tensile strength should, if practicable, or, at least, as far as may be practicable, be rigidly enforced on manufacturers. It would be a great boon not only to the engineering profession, but to the public generally, were it possible to ascertain definitely the tensile strength of a specimen of iron or steel with the same facility as the density may be ascer tained, and without the expensive and laborious, and, after all, uncertain, operation of the proving machine. We hope it will not be long before the progress of science will enable us to attain to this result. The Sand Patch Tunnel on the Pittsburgh and Connelsville Railroad is at last cut through. Its total length is 4,750ft., being 1,000ft. more than the long tunnel on the Pennsylvania Central Railroad through the Alleghanies between Altoona and Cresson. It is intended for a double track, and is 22ft. wide by 19ft, in height. ΜΕ been sufficiently reduced is bolted or sifted, while IMPROVEMENTS IN GRINDING MILLS. reduced to powder, into a pipe L, from which it The material to be operated upon is fed through an opening H in the side of the outer casing A, and the revolving arms G grind or crush it against the inside of the ring B, to which a slower rotary motion is simultaneously imparted by means of the pinion C, which is mounted on a shaft I. For operating upon substances of large size the inventors employ ribbed rollers or orackers K K, as shown in the plan view, fig. 4, or other breaking apparatus in proximity to the mill before described, so that the substances may be broken up before entering the mill; these rollers or apparatus may also serve to feed the substance regularly to the mill. The blast created by the revolving arms G in AR ORNAMENTAL GRILLING APPARATUS. room in which it is placed. At the back of the and for the general ventilation of the dining fire there is provided a self-acting arrangement, which effectually prevents the boiler flue becoming choked, and also for adjusting the ascending draught of the fire until the proper current has been obtained. The "grid" is manu. factured of polished steel thickly coated with silver, the part not in contact with the fire being solid silver, while the general design of the whole apparatus is carried out in bright steel, ormolu, and metallic electro, in such a way as to harmonise with the highly decorated style of a first-class public dining-room. It has been manufactured for a restaurant in Liverpool, where it will be despatched in a few days. Messrs. Jeakes are the originators of these handsome apparatus for dining-rooms, the "grills" at the Victoria and Ludgate Hill Stations, and the Exchange Buildings Birmingham, being amongst their productions. While upon this subject we may notice an im proved steam closet for cooking potatoes, which is constructed to cook 3 cwt. of potatoes in an hour. It consists of two compartments, one for wet steam and one as a hot closet for drying off after cooking. There is an outer steam jacket formed over the whole which is heated by the spent steam after leaving the wet compartment, and before being collected into a condenser under the apparatus. The whole process of cooking and heating the closet is carried on with steam at a less pressure than 1lb. per square inch, and the potatoes are perfectly cooked in 15 minutes, and thus the greatest economy is secured. A steamtight joint is effectually made for the doors by a simple contrivance, and the whole is under the most perfect control by regulating valves to the different parts and safety valves for the indication of too great pressure. The apparatus is mounted on an open cast-iron stand, with a provision for carrying off the condensed water that necessarily runs from the doors when opened. FIG. 4. FIG. 3. VAN BRUYSSEL'S ELECTRIC CLOCK. ELECTRIC CLOCKS. FIG. I. BL FIG. 2. hydraulic test, to be so rigid as to prevent the The boiler burst at the unguarded manhole, eight rents starting from it, which ripped up the shell into fragments, and tore them away from the furnace tube, which was left uninjured. The manhole cover, which faced towards the stern of the ship before the explosion, was shot through negative current, and as their positions with re the sides of a poop cabin in that direction, spect to the springs of each pair with which they while the main portion of the shell recoiled to. come into contact are alternately reversed, a posi-wards the bow, and embedded itself in a deck. tive and a negative current will be alternately house, the domed crown plate of the shell being transmitted to the distant time indicators. We thrown upwards, and afterwards found on the have recently inspected a number of clocks which deck of a neighbouring vessel, while the bulwarks and from the simplicity of construction and cer- appearance of having been in action. Added to are working upon M. Van Bruyssel's principle, were so splintered that they presented the tainty of action of the whole system, we think this, five men were laid dead on the deck, and it is one which deserves the attention of those two others blown overboard, while another was who have the regulation of public time, whilst so seriously injured that he lingered but a day or it only requires to be better known to come into se before he died. The sight of the dead bodies general use. laid out on deck, and the boiler plates bathed in their blood, is described as perfectly sickening; and reference to these facts is made that the disCONSTRUCTED STEAM astrous consequences may be appreciated of turning out improperly-finished boilers, the im A NEW system of working clock with great the arbor of the minute wheel. This gearing BOILERS. consideration of the direction in which the fragments of the boiler were thrown, the manhole portion of the shell recoiling in the other, if cover being shot in one direction, and the main taken in conjunction with the original position of the boiler prior to explosion, as well as with the eight rents which radiated from the unguarded manhole, prove incontestably that it was at that unguarded manhole the boiler first gave way. N his last report, the portance of which is so sadly overlooked. A Manchester Boiler Assefatngineer of the following interesting particulars relative to the explosion which occurred in one of our large commercial ports at about three o'clock on the afternoon of Tuesday, October 9th, to a small portable boiler employed on board a sailing vessel in driving a winding engine for hauling on board the cargo. This explosion is of a most melancholy character, not simply from the fact of eight persons having been killed, but from their deaths being perfectly gratuitous, since they arose from the improper construction and equipment of the boiler, which might easily have been corrected; while two other men were killed as recently as the 21st of April last by a similar boiler, which was turned out by the same maker, and burst from a precisely similar cause. The boiler, which was not under the inspection of the association, was of about 4-horse power and of vertical construction, baving an internal conical firebox containing two horizontal water tubes running across it. Its size was quite diminutive, which it is important to notice in connection with the very fatal results of the explosion, since the danger of small boilers is apt to be overlooked. Its height was only about 5ft. 6in., while the diameter in the shell was but 2ft. 6in. and in the internal furnace 2ft. at the bottom and 6in. at the top, the thickness of the plates being in. in the shell and 3-8in. in the furnace tube, while the working pressure was about 1001b. on the square inch, the bursting strain, as stated by the makers, being as high as 500lb. The cause of the explosion was made a matter of the most searching investigation by the coro. ner, who indefatigably pursued the inquiry for three entire days. Neither the makers of the boiler, however, nor the intermediate party who had sold it to the shipowners, were present at the inquest, both excusing themselves on the plea of illness, but the makers were represented by their lawyer, as well as by their manager. In their defence they attempted, as is usual in these cases, to throw all the blame upon the poor engineman who had been killed by the explosion. The legal gentleman tried hard to prove that the engine. man had allowed the furnace tube to be laid bare and overheated, through neglecting his feed, and that water must then have been dashed upon the hot plates, either from the sudden introduction of the feed, or starting of the engine, in conse. quence of which an excessive and uncontrollable pressure of steam had been instantaneously generated, which burst the boiler into fragments with the force of an ignited charge of gunpowder. It may be questioned whether such consequences would have resulted even if the furnace tube had The equipments of this boiler were defective been overheated as supposed, since the feed water both in the case of the manhole and safety-valve. was pumped into the boiler at the bottom, or nearly The manhole, which measured 13in. horizon. so, so that it could only have submerged the furtally by 10in. vertically, was not strengthened nace tube little by little as it rose and cooled it as it should have been with a substantial mouth- down gradually, which could not, it is thought, piece, nor even with a wrought-iron ring, but had have produced any rapid generation of steam. an ordinary internal cover, held up by one or two In support of this a case mentioned in a previous bolts suspended from arched bridges, notwith-report may be referred to, in which water was standing the high working pressure and the pumped into a red-hot boiler without having any lightness of the plates already described. The other effect than so straining the seams from safety-valve arrangement was most objectionable. violent contraction that they leaked like a sieve, Every boiler should have two good valves, whereas this had but one, and that of a most dangerous class. It was fitted with a spiral spring, which proved, on being submitted to a most careful and the water ran out of the boiler faster thau the engineman could pump it in, which was the first intimation he had of anything being wrong. These remarks, however, must not be misunder. |