« EelmineJätka »
globe, the operations of reading and writing occur in our own land. Such, however, has can be carried on with perfect facility at an been the case. The great earth wave has made elevation which reaches above the clouds. its vibrations felt at our own doors, and the
So long as the clouds are held in suspension puny, although highly effective, representaMECHANICS' MAGAZINE. by an upward current of air, they are either tions of man at the Polytechnic Institution
immovable, or they rise; when the current possess a real meaning to our west of EngLONDON: FRIDAY, NOVEMBER 6, 1868. fails, they fall. M. Flammarion gives a vivid Iand friends. The recent shock was very
account of the formation of the clouds over distinctly felt about twenty minutes before
the valley of the Rhine, viewed from an alti- eleven o'clock last Friday night, and it exUP IN A BALLOON.
tude of 7,000ft. above the historical town of tended over a considerable area in the west N a very short space of time, anyone who Aix-la-Chapelle. The sun rose at about a of England and South Wales. It lasted for regarded as a man behind the age, and will commenced to form underneath the observers, tions was said to have been very severe, be ranked in the same category as one who at a distance nearly half way between them whilst in others it is described as being but has never been in a “ Hansom or on a rail- and the earth. Shortly afterwards, the earth, slight. The night on which the shock occurred way. It is, in short, the proper thing to do, which had been distinctly visible hitherto, was cloudy but light, the moon being nearly and it will altogether depend upon the pro
became hidden from view by immense fleecy at the full. Taking the various accounts that clivities of the aeorostat whether he makes masses, which congregated at one point and have appeared from observers of the phenohis atmospheric voyage with scientific or dispersed at another with astonishing rapidity. menon, we find its indications variously demerely commonplace intentions. If with the With the rising of the sun, and the consequent scribed. Some describe it as a trembling of latter solely, he will be amply repaid by the increase of temperature, the balloon mounted, the earth, as a laden waggon was passing panorama spread out beneath his view. The and the clouds likewise, until the latter along the street ; others imagined some anicoup d'æil will be beyond his most sanguine arranged themselves immediately underneath mal had got in their bedroom and was scamexpectations, and he will return to terra firma the former, and, after remaining a short time, pering about the floor. The motion of at least a wiser man than when he quitted it. disappeared with tlie same celerity with which articles of furniture, the jingling of glasses, Our intention in the present article is not to they were created.
and the oscillation of beds, were very comdilate upon the interesting features that may
Leaving what we may call the lower mon. Most of the reports agree that these present themselves to the eye of the amateur, regions, namely, those of the cumulo-stratus, indications were accompanied by a noise like but to record some of the phenomena that and soaring into the space beyond, the that of a high wind, or of a vehicle or train attract the attention of the satan, the chemist,
" cirrus" appear to be as far above the passing. Reports from towns and villages and the philosopher. Meteorologists have observer as if he had not left the terrestial westward of Worcester describe the shock reduced the various conditions and
surface. One seems to be, as it were, in very similar terms. In Leamington, three
appearances afforded by the clouds and the regions between two skies, one above and the other shocks followed each other in rapid succesof air into nine distinct subdivisions. M. below. At an elevation of 13,000ft., the supe- sion. The shocks were noticed by Dr. Flammarion, in an exceedingly interesting rior vault loses its concave appearance, and O'Callaghan, LL.D., the president of the paper read before L'Academie des Sciences, the inferior appears to solidify, With a clear local philosophical society, who, during a has further reduced these subdivisions to two. atmosphere, the earth, instead of presenting residence in the West Indies, had on more He designates the clouds that appear nearest a convex form, has, on the contrary, a con- than one occasion felt the shock of earththe earth, or what we terrestrials would call cave surface. That the clouds are due to the quakes. On Friday night, Dr. O'Callaghan the clouds proper, by the name of cumulo- condensation of the humidity existing in the called attention to the occurrence, and found stratus. These viewed from a balloon re- air, is the result of all the meteorological ob- that the shocks had been observed by some semble large masses of grey vapour, or
servations made with the view of ascertain of his domestics. At Exeter, many persons gigantic bales of cotton. Under the second ing the nature and origin of their formation. noticed the earthquake. Three distinct classification of cirrus, be includes the small Currents ascending from a humid region, and shocks were felt by the inmates of a house in light fleecy-looking clouds that are pendent traversing a certain zone or belt, have their York-buildings. The occupant of a house, high up in the blue vault of the firmament, humidity condensed and rendered visible, who has long resided in the West Indies, slightly tinged towards the evening, some
which was previously invisible. A very recognized the shaking as that of an earthtimes of a dappled appearance, and at others curious phenomenon has been observed from quake. The inmates of the Eye Infirmary streaked with a rosy irridescence. We may
the elevated position of a balloon, and re- felt the building shake, and experienced a omit all consideration of the "stratus," which corded by M. Flammarion. During one of his peculiar sensation at the time. are visible only in the daytime, and the aerial yoyages his attention was attracted to
Reports from Merthyr state the shock to “nimbus," which are the forerunners of the a cloud, about 600ft. in length by 450ft. in dissolution of snow into rain. breadth, which remained in a state of im
have been rather severe, the movement apConfining ourselves, therefore, to the two de- movable suspension at an elevation of nearly pearing to be from south to north and con
A few scriptions of aeriform phenomena that we have 300ft. above some trees. The other clouds tinuing for three or four seconds. mentioned, it has been determined that the in the meantime were passing at the rate of minutes before the occurrence there was that first, the cumulo-stratus or clouds proper, are
25ft. per second. What invisible anchor held strange calm prevalent which has been noticed situated at an average distance from the this particular mass of vapour from partici- during the time of a complete eclipse. Great
At earth of 4,000ft. They are occasionally met pating in the motion of its neighbours ? alarm was felt by the inhabitants. with both above and below this distance. Upon steering the ballcon below the object Twynrodyn and other high quarters, the The cirrus or superior clouds are rarely to be of observation, it was discovered that the people rushed out of the houses, some attri
buting the shock to explosions underneath found nearer to the earth than 20,000ft. It cloud was stationary immediately above a
in has long been a problem to the philosopher Clouds, also immovable, traced out in space tum exists there, this fact was conclusive that large piece of water, and that some smaller
some coal or mine pits ; but as Merthyr to ascertain what thickness of cloud was the course of a stream.' No explanation has
is not undermined, and no mine or coal stranecessary to obstruct the rays of the sun. been offered of this curious fact, but it is the disturbance proceeded from a greater and the sun was obscured for some time after possible that some attraction may exist mysterious cause. commencing the ascent, but after continuing which they are created. The physical con- Wales. He says:-"The night was wet, with between the clouds and the sources from report from a meteorologist of some years
standing, who writes from Port Talbot, South to rise until the belt of clouds was left below, their thickness was ascertained to be about tours of a country are readily distinguished
He can tell at
a drizzling rain, and a strong S.W. wind blow620ft. The light of the sun was therefore by the experienced aeronaut.
Soon after unable to traverse this mass of cloudy opacity: tints they present to the rising sun.
a glance the plains and the valleys by the ing. Barometer stood at 29.50.
10 p.m. the wind abated; then followed a The degree of humidity registered by the hygrometer was a maximum at the lower surplains are dark and shadowy, while the lull, with an overcast sky: At 10-35 p.m., as
I was sitting with a friend in my drawingface of the mass of clouds, and a minimum at the valleys whiten and glisten heneath its beams. upper, the range being rather more than 5deg. and the thermometer invariably registers a
room, on the ground floor, suddenly we exThis is caused by the condensation of vapour, perienced a ead, heavy thump, as if from At the same time, the temperature obeyed a very lower degree for the valleys than the plains. side the window, followed, after the interval
the fall of a bale of goods close outdifferent law. Marking 20deg. at the ground with increased facilities for observing the level, the thermometer descended to bdelege condition of the upper regions at various of a second, by, a tremulous motion through regions of clouds, it rose to 19deg., and con- that a large augmentation will be made to
times and seasons, it is only to be expected feet, and rattled some ornaments on a side tinued to rise as the elevation increased. The aerial voyageur, when emerging from the
our present knowledge of meteorology, the table, the shock passing from N.W. to S.E., misty, gloomy, and melancholy æther of the bygrometrice state of the atmosphere, and time. The effect upon me and my friend was cloudy belt into the upper regions, experi- ultimately of the key of all science, astro
unmistakable. We at once exclaimed, “An ences a joyful and exhilarating sensation nomy.
earthquake!' My house stands alone on a which is perhaps enhanced by observing that
hill, with gardeners' cottages near. My serthe earth which he has quitted appears to be
AN EARTIIQUAKE IN ENGLAND.
vants, who were in their bedrooms, ran out lost in the shadows of night. This is no YONVULSIONS of Nature have been to know what was the matter, and those down darkness has descended upon the terrestrial l but one suspected they would ever cause of the noise. My gardeners and their
families were similarly surprised, but felt it be said with much success. The incessant about a minute, or with three men may be could be no other than an earthquake. I find jar and vibration that a permanent way is opened in less time. We are informed that that people who were out of doors at the time subject to appears to set at defiance all means one man has actually opened the bridge in did not feel the shock."
hitherto applied for practically overcoming two minutes. The contract for the general the inconveniences it gives rise to.
ironwork of the bridge was taken by Messrs.
The double-headed rails are more readily Finch and Heath, Chepstow, who were the DOUBLE AND SINGLE-HEADED removed and replaced than the Vignoles, for builders of Brunel's celebrated bridge at RAILS.
as they are not directly fastened to the Chepstow, and appears to be well carried out.
sleepers, all that is necessary is to knock The hand railing is being executed by Messrs. YHE contractors' or Vignoles rail is un- away the keys and fastenings and lift them Harris and Son, of Marsh-street, Bristol. it requires no chairs or keys of any kind. It are readily substituted for the worn-out ones, is, therefore, not surprising that many com- as sleepers and chairs can be removed panies give it the preference in their perma- together, while another, with its chairs fixed
THE CIVIL AND MECHANICAL nent way, particularly when the road is laid on, can be slipped in at once. M. Séverac ENGINEERS' SOCIETY upon transverse sleepers. At the same time, states, in support of his prediliction for the
N Saturday last, the first annual dinner its supporters also. The objections alleged not present so many difficulties as the flar.ged Anderton's Hotel, Fleet-street, a goodly numagainst the latter are that, in the first place, example, and that therefore it can be obtained ber of members and visitors attending. it necessitates the expense of chairs; and cheaper in the iron market. We have doubts Amongst those present were the following that, secondly, the turning of them, in which respecting this assumption, and are inclined Members of Council – Mr. B. Haughton, Pretheir chief merit lies, cannot be accomplished to believe that the price per ton would not sident; Mr. W. F. Black, Vice-President; universally. If every rail could always be vary to any extent worth consideration. Messrs. F. Cooper, W. Meakin, R. M. Banturned, so as really to do the duty of two, There is, however, truth in the observation croft, G. W. Usill, G. W. Willcocks, F. H. then the increased amount of work got out of that the double-headed rail is better adapted Roberts (hon. sec.), and G. J. Dawson (hon. the rail would more than compensate for the for sharp curves, owing to the greater facility treasurer). Amongst the members present expense of the chairs, and, cæteris paribus, it possesses for being bent to the required were Messrs. G. E. Eachus, G. R. Godson, it would prove more economical than the radius. The flange of the Vignoles rail, by T. Kell, A. II. Lavers, H. G. Powell, G. H. flanged description. To effect this result, its comparative large breadth, bends with Royce, R. T. White, J. B. Walton, &c.; and two precautionary measures must be under- difficulty, and incurs a greater chance of amongst the visitors were Messrs. F. A. taken,—the one to prevent the unevenesses being weakened and damaged by the opere- Klein, N. P. Burgh, J. Manners, A. Yarrow, and asperities which are produced upon that tion. Most of the steel rails rapidly coming portion of the rail in contact with the chair; into extensive use are of the double-headed patriotic toasts had been given and heartily
Blundell, &c. After the usual loyal and the other, to enable the upper head, after form. In this, as well as in other similar being worn; to bed evenly and steadily in the matters, engineers must be guided by their responded to, the toast of the evening, “Succhairs. With the ordinary chair these con- own experience and judgment; and where the
cess to the Society," was proposed. The ditions are not accomplished. The wooden merits of either side are pretty evenly balanced, the Society, which it may not here be out of
response brought out some facts concerning keys which are employed to wedge the rail as in the present instance, we must expect to place to reproduce. First, then, we learn against the chair allow a small separation to witness advocates upon both sides.
that the Society has been in existence for exist under the varying circumstances occasioned by the influence of the weather. Con
nearly ten years, and now consists of twelve
honorary members, nine life members, and sequently, the passage of a train produces a successive repetition of little shocks or con
THE NEW SWIVEL BRIDGE AT
seventy-five ordinary members. Its meetings cussions, which give rise, after a certain length
are held on the second and fourth Wednesday
in each month, from October to June incluof time, to a notching in the lower head of the rail which rests upon the chair. M. A
NEW swivel bridge was opened last sive. The next meeting will be held on the
month at Bristol, and which possesses 11th inst., when a discussion will take place Séverac, a French engineer, proposes to obviate these difficulties by the adoption of a the bottom of Clare-street, and opens on to which we purpose placing before our readers
some noteworthy features. It is placed at upon the President's address, an abstract of chair differing but very slightly in its con- St. Augustine's Parade, a point where a bridge next week. The papers read are purely of struction from those in ordinary use. In
has always been necessary. Formerly, a a scientific character, and the Society are FIG.I.
wooden lifting or drawbridge stood there, about to take steps to publish their proceedwhich was in time replaced by one of im- ings. This association also possesses an inner
proved construction. This in its turn gave element, which renders it of especial value FIG.2. way to a still better design--a swivel bridge to the younger members. A species of inter
-by Mr. Gravatt, C.E., which, however, at communication is carried on amongst the length became dilapidated, and has now been members through the secretary, and at any succeeded by a newer and more commodious meeting a member requiring information structure from the designs of Mr. Howard, upon any knotty or doubtful point, places engineer to the Docks Committee. To have his question in the hands of the secretary, placed the bridge so oblique as to have been who elicits an answer from the meeting, with
exactly in line with Clare-street would have out, of course, divulging the inquirer's name. figs. 1 and 2 are shown the intended alterations. required the present pier of masonry re- On the whole, the Civil and Mechanical EnThe chair differs from that in common use by moved, and a new one built, and would, more- gineers' Society is a highly useful institution, having the size of the part B, in which the over, have placed the traffic towards St. and one which is well calculated to promote rail is bedded, larger, thus permitting the Augustine's-place at a great disadvantage. the interests of young aspirants to profeshead of the rail when turned to bed in it, A mean line, keeping the centre of present sional fame, being governed as it is by gentlealthough it may have become flattened and pier, was therefore adopted. In the present men of experience and sound practical knowlaterally increased in dimensions by the wear design, the system of a king post and sus- ledge. and tear it has undergone. In the chair, and pending rods, which gave the necessary underneath the rail, is placed a small cushion strength, but which took up a considerable
EXPERIMENTS ON ANEROIDS. C of hard wood, which is changed for another width, has been discarded, and the whcle surof a slightly increased thickness when the rail face made available for traffic. The roadway THEO: Poss contain" an account or certain et is turned. "By this arrangement, the rail will has been increased ift. 4in., and each of the shocks will be avoided, which frequently break of the bridge, with its counterbalance, is Committee,' by B. Stewart, LL.D., F.R.S., &c. always be securely and firmly bedded, and the footways 11in. in width. The total weight periments on aneroid barometers, made at Kew the chairs, and occasion a large amount of about 120 or 130 tons, which is carried partly We propose to place before our readers an unnecessary wear and tear to the permanent on four cast-iron chilled wheels running on abridged report of these experiments, and then to way and rolling stock. It is true that the an iron roller path, the crown of which is of add a few remarks of our own. In judging of the shocks will still occur, but as the rail is bedded cast steel. The greater portion of the weight value of an instrument, says the report, such as upon an elastic material, they will not have is, however, supported by the centre pivot, an aneroid, it is not the mere extent of difference any injurious effect. The cushions of wood on the top of which are fitted gun metal and between its indications and those of a standard should be treated with some preserving sub- steel discs, and on these the bridge turns. In barometer that ought to guide us ; but it is rather stance, such as creosote, and also subjected order to adjust the height of the bridge to the constancy of its indications under the various to a pressure, to condense and harden them. any settlements or wear in the adjoining circumstances to which it may be subjected, that They will in that state still possess a degree roadways, the centre bearing on the metal determinos its value. An aneroid may differ from be able to withstand the pressure and vibra- screw, llin. diameter, by which the whole vided these differences can be well ascertained of elasticity sufficient for the purpose, and discs is formed of a large hammered scrap iron a standard barometer at the ordinary pressure, and tion of the rail without being crushed or bridge can be raised or lowered. The old bridge and remain constant, such an instrument ought to altered in shape. The plan of introducing took six men about two minutes to open or be regarded as valuable, just as much as a chronoan elastic medium between tbe rail and the shut; the present one, in which the friction is ineter of known constancy, but of which the rate chair has been frequently tried, but it cannot reduced to a minimum, will take two men is wrong.
19in. 20in. 2lin. 22in. 23in. 24in. 25in. 26in. 27in. 28in. 29in. 30in.
10.+ 70.+ $0.+ 80.+ 80.+ 80.+00.
70.-10.-10.-70. + 10.+ 00.
The circumstances which may be supposed to 2. That small anoroids are less trustworthy than affect the indications of an aneroid may be classed large ones, and probably cannot be trusted below
Aneroid No. under three heads, namely :
3. That if previous experiments are made upon
8. 9. 10. 14. 16. 3. Sudden variations of pressure.
a table of corrections which, when applied to 1. Time. Of the influence of time, Dr. Stewart futuro observations with the same instrument, has no definite information to communicate ; there will most probably present us with a much botter Correction before fore, of course, what he does actually say is of no result than had we not verified our instrument at experiment - 10 -12 -12 -.04 - 05 value.
all, and that by this means we may use our instru- Immediately after 2. Temperature.-A good aneroid is generally ment down to 19 inches with very good results. experiment .00 +503 +:06 +:06 +.04 compensated by its maker for the effects of tem Readings of these instruments under increasing 18 hours after perature, and the question to be investigated is, pressure, after remaining an hour and a-half at the experiment --07-03 -.01 +:01 to what extent such compensations are trust- lowost reading, were recorded.
18 hours after worthy. I record the results of subjecting six The mean corrections for up readings are exhi experiment --08-.04 - 03 aneroids, each 4fin. in diameter, made by two bited in the following table, each aneroid being 3 days after exdifferent makers, to a very considerable range of supposed right at 19 inches :
periment -.08 - .05
... -.01 -01 temperature.
3 weeks after ex
periment - 13 - 10-11 -.07 -06 No. of
Correction at ment.
It thus appears that if an instrument reads 55° F. 72° F. 78° F. 100° F.
correctly before it is put into the receiver it will
read too low immediately afterwards, and that 2 - 105 - 135 -140-145 -145
it may be some considerable time before it recovers 3 --055 --090 -.095 --095 -100
its previous reading. The instrument cannot, 4 --095 --095 --095 --080 --060
therefore, bo safely trusted for absolute determina-106 -106 -111
tions if it has been recently exposed to rapid _-101 -111 --111 --106 - 106
changes of pressure. 7 -061
Tho experiments hitherto recorded, in which an
inch of pressure has been taken away or added Those results are, on the whole, very satisfac
every ten minutes, are perhaps analogous to ascents tory, and appear to show that a well-made com
in a balloon, or descents from a mountain; they pensated instrument has its indications compara
are not, however, precisely analagous to mountain tively little affected by a very considerable tem
ascents, since a longer time than ten minutes is perature change. It ought always to be borne in
usually taken to produce a change of pressure equal mind that an aneroid is not capable of being read
to one inch. to the same accuracy as a standard barometer, and
At the suggestion of Mr. Charles Brooke, a that the 1-100th of an inch is a very small
couple of aneroids were tested in April, 1868, with quantity. These temperature experiments were
the view of rendering the experiment more anamade at the ordinary atmospheric pressure. I am
logous to a mountain ascent. unable to say what effect a change of temperature
The pressure was reduced by half an inch at a would have at a diminished pressure.
time and at intervals of thirty minutos, the ane3. Sudden changes of pressure.-For the pur
roids being well tapped. pose of investigating the influence of sudden
The following corrections were obtained for changes of pressure upon the indications of ane
down readings (instruments supposed right at roids, I applied to some of the best known makers
thirty inches). of these instruments, for tho loan of soveral, and through their courtesy in lending me a sufficient
At No. 8. No. 9. number, and for a sufficiently long time, I have
At No. 8. No. 9. been enabled to investigate this influence at some
inches length. In the following experiments, the instru
inches 30 .00 .00 23:5
+:08 -.02 ments were, to begin with, suspended vertically, at
29-5 .00 03 23
- 03 the usual atmospheric pressure. They were tapped
29 .00 04 22-5
--01 before being read. The pressure was then lowored
28.5 .00 .03 22
.00 an inch, and the instrument allowed to remain ten
28 .00 --03 21:5 minutes at this pressure before being read, after
27.5 having again been well tapped. The pressure was
--02 21 +:17 +.04 27
20.5 thus reduced an inch every time, being allowed to
+.201 +.06 26-5 .00
20 remain ten minutes at each stage; the instrument We may learn from these results, says Dr.
26 was always well tapped before being read, by means Stewart, that if aneroids which have been subjected
19.5 +:25 1 +.09 of an arrangement contrived for this purpose by for at least one hour and a half to the lowest
--02 19 +27 +:11 25 +:05
-04 Mr. R. Beckley. The exhaustion was carried pressures which they register, have the pressure downwards to 19 inches, and the instrument was incrcased by means of the gradual introduction of
24.5 +:06 2+
-.01 allowed to remain an hour and a-half at its lowest air into tho receiver, after the manner already pressuro; the air was then admitted an inch at a described :time, the previous arrangement as to time and 1. That & well-constructed large aneroid will tapping being followed. not go far wrong for about 8 inches above the lowest determinations for those same instruments, would
These results, when compared with the previous Separating the results of the experiments into pressure. two sets, one comprising large (tin. to 4fin.) 2. That in this respect small aneroids are some when the exhaustion is carried on more slowly, and
seem to show that a somewhat better result is obtained aneroids and the other small instruments, we find what less trustworthy than large ones. the mean down correction to be as follows, each 3. That if the instrument read be previously able extent, on the nature of the treatment re
hence that the corrections depend, to a consideraneroid being supposed right at 29in. tested and its corrections ascertained we may con
From all these experiments, Dr. Stewart con
cludes as follows:29in. 28in. 27in. 26in. 25in. 24in. 23in. 22in. 21in. 20in. 19in.
A good aneroid of large size may be corrected for temperature by an opiician, so that the residual correction shall be very small.
If an aneroid correct, to commence with, be used Mean correction)
for a balloon or mountain ascent, it will be tolerably of two large -00 •00 +.02 +.03 +:04 +:04 +.07 +:11 +:14 +:19 +:25
correct for a decrease of about 6 inches of pressure. aneroids
A large aneroid is more likely to be correct than a small one.
The range of correctness of an instrument used Mean correction
for mountain ascents may be increased by a prefor four small .00 +.01 +.02 +03+:07 +.07 +09+:12 +:17 +.23 +:25
vious verification, a table of corrections being thus aneroids
If an aneroid have remained some time at the top of a mountain, and be supposed correct to start
with, then it will give good results for about 8 inches Wo see from these results, says Dr. Stewart, sider it trustworthy (making use of these correc- of increase of pressure. that if aneroids, right to begin with, be subjected tions) for up readings throughout a greater range A large aneroid is more likely to be correct than to a decrease of pressure similar to that to which than if it had not been so tested.
a small one. they were subjected in these experiments
If the aneroid has been previously verified, it is 1. That a well-constructed large aneroid will
I come now to consider whether a rapid change likely to give a better result. not go far wrong down to 24 inches, but after that of pressure affects an aneroid after the experiment
Aftor being subjected to sudden changos of prespressuro its reading will be considerably lower has been completed.
sure, the zero of an aneroid gradually changes, so than that of a standard barometer, so that a large The following table will exhibit the results ob- that, under such circumstances it onght only to be positive correction will have to be appliod. tained in this direction :
used as a differential and not as an absolute instru
For two large?
For four small
ICELAND MOSSANALYSIS OF WATERS.
ether. He also used nothing but cadmium salts in In Kingbam's work on photography we find the and, from that, brandy, from lichens. Iceland moss, gave a perfect image, the second was a little under- of the varnish on the plate be alcohol, chloroform, sugar by boiling with a dilute acid. A specimen passage of a cloud at the moment. A long sliding drop of each of these menstrua, to ascertain which glucose, which, when fermented and distilled, really obtained six pictures of the eclipse, two of the bottom of this box solder å ring of tin, about to chemists concerned in the analysis of waters
ment, that is to say, used to determine the distance the telescope by a tube of india-rubber. The quantity of the solvent on the outside of the supascended, making it correct to begin with, or to eclipse has been successfully observed in a clear port ; place the plate, collodion side upwards, on the ascertain the distance descended, making it correct sky, further east than India, by M. Stéphan, a ring, cover the box as nearly air-tight as possible to begin with, it being understood that the instru- French philosophor, who stationed himself at Wha- with a piece of glass, and place it in a water bath; ment ought to be quiescent for some time before Won, in the Malayan peninsula ; also by Captain the vapour of the solvent will soon cause the the change of pressure is made.
Reed, who observed it on the coast of Borneo. We varnish to swell, and the edges of the cracks to The results to which these experiments appear can hardly expect news from a more eastern district coalesce. As soon as this end in view is accomplished, to have led are certainly interesting, but they still, as the island of Papua is too far from civiliza- the plate is carefully withdrawn, and when cool is throw no new light upon the action of the aneroid. tion, and it is not easy to effect a landing on large again varnished with a similar varnish." All the peculiarities pointed out in this account portions of its coast, because they consist of long have been long known, and have been stated over banks of mud, almost perfectly flat. and over again. They are too perplexing for the Direct photographs of the sun and its spots are generality of people to trouble themselves about, taken regularly at Kew Observatory and preserved as
NOTES ON RECENT SCIENTIFIC DISand the consequence is that the aneroid for com- records ; some also, on a very large scale, have been COVERIES AND THEIR PRACTICAL APmon purposes holds a similar relation to a barometer taken by Mr. Warren De La Rue, F.R.S. Very PLICATIONS. that a Dutch clock does to a regulator. Among beautiful fac-similes of the best of these pictures A MODE OF MEASURING THE INTENSITY OF LIGHT-A thoughtful persons, however, these results thus have been drawn upon steel plates, and are now
STRONG STONE CEMENT-USES OF LIQUID AMALGAM onunciated will produce good effect, and they well published in a new and very good work on astro
OF ZINC IN GALVANIC BATTERIES-BRANDY FROM deserve the attention of the manufacturers of these nomy, by Mr. Norman Lockyer.* The same book instruments. It is a matter of regret that Dr. contains descriptions of the apparatus used by Mr.
N pensation for lower temperature and also under a of the stars, with illustrations. Much care has been may be at any time measured and registered, low pressure.
taken in getting up this standard little work, the is still wanting. Dr. Roscoe proposed, a year or It would not have been difficult to have con- author having been aided by several leading philo-two ago, to measure and register the intensity of structed an apparatus suitable for the purpose. As sophers experienced in the several branches of the light by means of photography. This is, however, regards the mere error of graduation, it is prob- science. The Royal Astronomical Society placed able that, if tho aneroids had all been placed with facilities at his disposal; so also did Mr. Warren De rather a measure of the chemical activity of light the dials horizontal during the investigation, a La Rue and Dr. Balfour Stewart, Superintendent of than of light itself. Mr. Kirkham has proposed quite different set of corrections would have been the Observatory of the British Association at Kew. the same moans of measuring the luminosity of a obtained. It is, therefore, an omission of some Some recent photographic experiments by Mr. gas flame. But this, again, is objected to, since moment not to have observed at all how the instru- George Dawson, M.A., of King's College, are of the light of gas is deficient in the chemical rays. ments indicated in horizontal as well as the vertical scientific interest. Three ounces of clippings from The simple instrument which has been devised by position. Why they were always tapped before a bar of perfectly pure silver were dissolved in Mr. Roger Wright, and has been recently described being read is not stated. We are at a loss for any pure nitric acid, and the slight excess of acid in tho “Proceedings” of the Royal Society, will serve reason for tapping them. In our opinion, it is un- removed by recrystallizing the salt many times, excellently well to moasure approximately the innecessary and injudicious. Neither is it stated from the purest of distilled water, over a sand tensity of total daylight for comparative purposes. whether or not the aneroid readings were compared bath. A negative bath was then made of this It consists of a solid rod of metal standing perpenwith the standard barometer readings corrected very pure nitrate of silver, which proved to be dicularly on a heavy base. The top of the cylinder for temperature. If not, then the increasing error very slightly alkaline to test papers, a peculiarity is painted white, with a black spot in the centre. for decrease of pressure is partly accounted for; always exhibited by this salt when it is absolutely A hollow tube, blackened inside, is made to fit but, if they were, then it seems that the makers pure. A plate was coated with an ordinary exactly, and slide over this rod. The rod is had not graduated them to accord with barometer slightly acid bromo-iodized collodion, and sensitized marked with a scalo beginning with zero at indications corrected for temperature. As this is in the bath. On trial in the camera, a foggy and the base. To use the instrument, the tubo what should be the practice, if it is not followed, it scarcely visible picture was the result, yet tho is pushed over the rod down to the zero point ; ought to have been inculcated.
samo collodion worked well in other baths. He it is then drawn gently up, the observer Those who use the aneroid for scientific purposes, then triod a very new and neutral sample of looking steadily at the black spot, and when the as for measuring heights, should never placo much bromo-iodized collodion in the pure bath." This spot vanishes in the gloom the point is read off on confidence on its accuracy. Its indications require gavo good and blooming negatives with an almost the graduated scale. The point will, of course, to be checked froquently with a standard barometer instantaneous exposure in the glass house. That vary with the intensity of the light, and thus a at the standard temperature, 32deg. Fah. The a neutral collodion and slightly alkaline bath measure of the intensity is obtained. errors of an aneroid are greatly more capricious should give good pictures is something entirely
Böttger informs us that a cement of extrathan the rate of a chronometer. Even to state now to photography, though the principle was ordinary binding power is made by msing infusorial that the aneroid may be used as a differential in- once laid down in a very unconvincing and com- silica in placo of quartz sand. strument is fallacious, or we do not know what is plicated manner by Mr. M'Lachlan. The same earth is found in Germany only, but it has been meant. It is not at all uncommon to find aneroids new and neutral collodion did not give good imported into this country in considerable quantireading half an inch wrong. To suppose such an pictures in the ordinary acid baths. If, after ties. It consists of hydrated silica, which combines instrument correct, when determining by it differ- further testing, these facts should be verified with bases much more readily than silica in the onces of elevation, is to suppose that equal differ- beyond all doubt, the discovery will be valuable in anhydrous condition, as in quartz sand. The inencos of pressure throughout the atmosphere are astronomical photography, for the slight trace of fusorial silica is mixed in about equal proportions exponents of equal differences of elevation, which acid usually given to secure clean pictures has a with oxide of lead; about half a part of freshly is not true.
slight retarding influence, and necessitates a slightly slaked lime is then added, and the whole is made longer exposuro.
into a paste with boiled linseed oil. The cement PHOTOGRAPHY.
In rapid photography, where the exposure re- thus made quickly becomes as hard as sandstone,
quires to be reduced to the smallest possible frac- and will be found extremely useful in such work THE SUN-ASTRONOMICAL. tion of a second, slight influences like these have as fixing iron in stone for balusters and railings.
not likely, we think, to expand in setting, and STANTANEOUS PHOTOGRAPHY——CRACKS IN NEGA- not scientifically and accurately known. Celestial thus no risk of splitting the stone will be incurred.
photography will not be brought to perfection till In this respect alone it offers a great advantage SINCI INCE the first news reachod England of the many obscure phenomena of this kind have their over Portland cement, sometimes used for the
work of Major Tennant, R.E., in photograph-accelerating and retarding powers determined by purpose we have mentioned, which, according to ing the total eclipse of the sun at Guntoor, he has stances, these slight influences are unnoticed and of which one very serious accident is supposed to made enlarged copies of some of the negatives then unknown, because they do not interfere appreciably
have resulted. obtained. Although, as we have previously stated, with the results,
Fortin has recently proposed to use a liquid the original negatives were faulty, still some of
Many bad photographic varnishes constantly amalgam of zinc in galvanic batteries in place of them not only show the flamo prominences, but most disastrous effect upon the pictures, cracking The advantages are said to be a saving of the
creep into the market, and some of them have that metal alone or only superficially amalgamated. streaks in them, spiral in form. Dr. Vogel, who valuable negatives all over, and rendering them trouble of shaping the zine, and greater constancy very successfully photographed the total phaso at worthless. We know an amateur photographer of power from the ease with which the sulphate of Aden, used a bromo-iodized collodion, which also who, after a tour of a few weeks in Wales, taking zinc can be removed as it is formed. We are not contained an excessively large proportion of alcohol, his negatives cracked all over by a miserable is disposed, but as soon as we receive the informa
pictures of beautiful sea coast scenery, had half yet told the exact way in which the liquid amalgam to render evaporation less rapid in a tropical climate sample of varnish. When such cracks are very
tion we shall give it. than if the collolion contained the usual amount of fine, the negative will sometimes print well if a
Among the curiosities of chemistry we may little plumbago be gently brushed into the cracks. mention the production in Sweden of grape sugar, the collodion: The developer consisted of ammonio, following little-known remedy for the evil, and if for oxample, which is found in Sweden, in large wator 102 parts. Of the three plates exposed, one valuable : 25 First ascertain whether the solvent as well as the cellulose, is converted into grape exposed, and the third was a failure because of the
or benzole, by dropping on one corner a minute of Iceland moss gave as much as 72 per cent of back was used in the telescope camera, to allow dissolves the varnish. Next take a tin box some
yielded a brandy having a very-agreeable flavour. two pictures to be taken on one plate, so that he what larger than the picture, about lin. deep; at
It will be interesting as well as novel information which were failures. The photographic parts of
that M. Bechamp considers he has established that his apparatus were not directly attached to the Lin. wide, of the same shape and nearly of the same telescope, because the insertion of the slides might sizo, as a support for the glass plate ; pour a small in sulphuretted waters, containing, as they supotherwise set up vibrations, so the camera was
pose, alkaline sulphides, the sulphuretted hydrogen fixed upon a separate stand, and connected with LOCKYER, F.R.A.S. London: Macmillan and Co, 1868.
• " Elementary Lessons in Astronomy." By J. NORMAN and the alkali are not in combination, but remain
free, although in the presence of one another,
THE GREAT ECLIPSE OF