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Philosophical Magazine, for October, 1840, The following is the process at present I mentioned some instances in which I had adopted by me, which I consider far from copied printed pages and engravings on perfect, but which affords us very delicate iodized paper, by mere contact and exposure images. to the influence of the calorific rays, or to A well polished plate of copper is rubbed artificial heat. I then, speculating on the over with the nitrate of mercury, and then probability of our being enabled by some well washed to remove any nitrate of copper such process as the one I then named, to which may be formed ; when quite dry å copy pictures and the like, proposed the little mercury taken up on soft leather or name of Thermography, to distinguish it linen is well rubbed over it, and the surface from Photography.

worked to a perfect mirror. 18. I now tried the effects of a print in The sheet to be copied is placed smoothly close contact with a well polished copper over the mercurial surface, and a sheet or plate. When exposed to mercury, I found two of soft, clean paper being placed upon that the outline was very faithfully copied it, is pressed into equal contact with the meon the metal.

tal by a piece of glass, or flat board; in this 19. A paper ornament was pressed be state it is allowed to remain for an hour or tween two plates of glass, and warmed; the two. The time may be considerably shortimpression was brought out with tolerable ened by applying a very gentle heat for a distinctness on the under and warmest glass, few minutes to the under surface of the but scarcely traceable on the other.

plate. The heat must on no account be so 20. Rose leaves were faithfully copied great as to volatalize the mercury. The on a piece of tin plate, exposed to the full next process is to place the plate of metal in influence of sunshine, but a much better im. a closed box, prepared for generating the pression was obtained by a prolonged expo vapour of mercury. The vapour is to be sure in the dark.

slowly evolved, and in a few seconds the 21. With a view of ascertaining the picture will begin to appear ; the vapour of distance at which bodies might be copied, I mercury attacks those parts which correspond placed upon a plate of polished copper, a to the white parts of the printed page or enthick piece of plate glass, over this a square graving, and gives a very faithful, but a of metal, and several other things, each somewhat indistinct image. The plate is being larger than the body beneath. These now removed from the mercurial box, and were all covered by a deal box, which was placed into one containing iodine, to the more than half an inch distant from the

vapour of which it is exposed for a short plate. Things were left in this position for time; it will soon be very evident that the a night. On exposing to the vapour of iodine vapour attacks those parts which are mercury it was found that each article was free from mercurial vapour, blaekening them. copied, the bottom of the deal box more Hence there results a perfectly black picfaithfully than any of the others, the grain ture, contrasted with the grey ground formed of the wood being imaged on the plate. by the mercurial vapour. The picture being

22. Having found, by a series of experi formed by the vapours of mercury and ments, that a blackened paper made a iodine, is of course in the same state as a stronger image than a white one, I very an Daguerreotype picture, and is readily dexiously tried to effect the copying of a printed stroyed by rubbing. From the depth to page or a print. I was partially successful which I find the impression made into the on several metals, but it was not until I used metal, I confidently hope to be enabled to copper plates amalgamated on one surface, give to these singular and beautiful prodocand the mercury brought to a very high tions, a considerable degree of permanence, polish, that I produced anything of good so that they may be used by engravers for promise. By carefully preparing the amal working on. gamated surface of the copper I was at It is a curious fact that the vapours of length enabled to copy from paper, line mercury and of iodine 'attack the plate differengravings, wood cuts, and lithographs, with ently, and I believe it will be found that vapours surprising accuracy. The first specimens have some distinct relation to the chemical, produced, exhibit a minuteness of detail and or thermo-electrical state of the bodies upon sharpness of outline, quite equal to the early which they are received. Moser has ob. Daguerreotypes and the Photographic copies, served this, and attributes the phenomena prepared with chloride of silver. *

to the colours of the rays, which he sup

poses to become latent in the vapour on its • The first faithful copy of the lines of a copper passing from the solid into the more subtile plate engraving was obtained by Mr. Cantabrana, who has since succeeded in procuring some tolera

form. I do not however think this explanable specimens, on uuamalgamated copper, which

tion will agree with the results of experiments. cannot be rubbed oil.

I feel convinced that we have to deal with

some thermic influence, and that it will MR. SAMUEL HALL'S PATENT CONDENSERS. eventually be found that some purely calorific excitement produces a molecular change, or

Report of Sir W. Edward Parry and that a thermo-electric action is induced,

Messrs. Ewart and Lloyd to the Lords which effects some change in the polarities

of the Admiralty. of the ultimate atoms of the solid.

In pursuance of Sir George Cockburn's These are matters which can only be de minute of the 19th of February, 1842, on cided by a series of well conducted experi the statement accompanying Mr. Samuel ments, and, although the subject will not be Hall's note of the 7th February, we beg laid aside by me, I hope the few curious and leave to submit the following report, founded certainly important facts which I have brought upon all the information which could be before you, will elicit the attention of those obtained respecting the results of the appliwhose leisure, and well known experimental eation of Hall's condensers to vessels now talents, qualify them in the highest degree in her Majesty's service; and upon consifor the interesting research into the action deration of the present condition of the conof those secret agents, which exert so power densers of the Megera, and the effects which ful an influence over the laws of the material this system of condensation appears to have creation. Although attention was called to produced with regard to the consumption of the singular manner in which vapours dis fuel, and the condition of some parts of her

osed themselves on plates of glass and engines and boilers. copper, two years since by Dr. Draper, Having understood that Hall's condensers Professor of chemistry at New York, and had been tried in several steam-vessels beabout the same time to the calorific powers longing to the St. George Company, and of the solar spectrum, by Sir John Herschel,* subsequently removed from them, Com. and to the influence of heat artificially ap mander Bevis was directed to make special plied, by myself (17) yet it is certainly due inquiry as to the circumstances attending to M. Moser of Konigsberg, to acknowledge such removal. By Commander Bevis's rehim to be the first who has forcibly called port of the 10th of March (enclosed herethe attention of the scientific world to an with), it appears that these condensers were enquiry which promises to be as important applied to six vessels, and removed from in its results, as the discovery of the electric them after a trial varying from two to six pile by Volta.

years, in consequence, as it is acknowledged, As to the practical utility of this discovery, of their complicated construction, and the when we reflect on the astonishing progress difficulty of keeping them in order. This made in the art of Photography since Mr. is entirely at variance with the experience Fox Talbot published his first process, what afforded by the Megera during a trial of may we not expect from Thermography, the four years, during the last three years of first rude specimens of which exhibit far which the condensers were never even opened greater perfection than the early efforts of for inspection, and they are now in good the sister art?

condition. The report of the engineer As a subject of pure scientific interest, officers of Woolwich Yard, dated 11th of Thermography promises to develope some of March (transmitted herewith), is conclusive those secret influences which operate in the on this point. mysterious arrangements of the atomic con Although in ordinary cases the vacuum is stituents of matter, to show us the road into better with Hall's condensers than with the yet hidden recesses of nature's works, those of common construction, it is necesand enable us to pierce the mists which at sary to state that we have been informed present envelope some of the most striking that in tropical climates, where the temperaphenomena, which the penetration and in ture of the sea water used for condensing the dustry of a few " chosen minds” have brought steam is high, the process of condensation before our obscured visions. It has placed is less perfectly performed by Mr. Hall's conus at the entrance of a great river, flowing densers than by the common ones. into a mighty sea, which mirrors in its glow. plication has been made to the East India ing waters some of the most brilliant stars Company to furnish any facts which might which beam through the atmosphere of throw light on this part of the subject, but truth.

they do not at present possess the required ROBERT HUNT.

information. If, however, this difficulty

should be found to exist in a tropical cliPalmouth, November 7, 1842.

mate, we think it probable some means of

obviating it might be devised. Philosophical Transactions, Part 1st for 1840,

To ascertain the saving of fuel, we have Page 50.

made the comparison between

the consumption of the Megera and the Volcano. The

An ap

1

Mean ......

boilers of the Volcano are of copper, and should not estimate too highly the annual those of the Megara are of iron, with Hall's saying in repairs at 1501., which with the condensers; in other respects the vessels are estimated value of the saving in fuel, would alike. From the accompanying account it amount to 6751. will be seen that the average daily consump The first cost of the patent condensers, tion of fuel on board these vessels has been according to the statement of Messrs. Sea. obtained in two ways, perfectly distinct from ward and Capel, is from 71, to 81. per horse each other :

power ; according to Mr. Hall it is from 51. First, by ascertaining from the logs of to 101. per cent. upon the cost of engines the respective vessels the number of days in and boiler, or from 2 to 51. per horse which the engines were at work, and com power. In conclusion, it may be remarked paring it with the total quantity of fuel ex

that Hall's condensers are calculated to ena. pended. Secondly, by taking an average of ble a vessel to run without repairs for a the consumption of fuel per horse power longer time than common condensers; but per hour, as reported by the commanders in to what extent we have not had sufficient exthe monthly, returns.—The average daily perience to enable us to state with any consumption in the

degree of certainty. Tons.

W. E. PARRY. Megera was, by the first mode.. 14 507

P. EWART.
second mode 13 41:56

T. LLOYD.
Mean ...... 141
Volcano was, by the first mode.. 17 13.60

second mode 18 4.5
18

WIRE ROPE LIGHTNING CONDUCTORS. --showing a saving per day of 3} tons, or Sir,- It is a pity that your correspondent nearly 20 per cent. ; or if, as an approxima Mr. J. R. Hill does not take the trouble to tion, the vessel be supposed to run 150 days make himself acquainted with all facts bearin the year, and the cost of the coal be

ing upon a subject, before he writes on it; had estimated at 208. per ton, the saying in the he done this, he would not, I am sure, bare cost of coal would amount to 525l, per taxed me with claiming an invention as my

own, without having troubled myself to The comparative consumption of fuel in

carry it out.

It is now many years since I these two vessels could not materially differ not only “suggested" wire rope conductors from what is here given, but we are not pre for ships, but also " encountered much diffipared to say that this great saving is entirely culty, disappointment, and expense,” in en. to be attributed to Mr. Hall's condensers. deavouring to bring this lightning conductor Some part might have arisen from the com into use: this, I believe, is well known to most manders constantly evincing a strong desire electricians of the present day, and were it to economise the fuel, and from the care and necessary, I could refer Mr. Hill to persons judicious management of the engineer. A and documents, private, as well as connected considerable saving, however, must, we with the government, that will bear me out, think, always obtain, from there being no and that my plan provided for a perfect con. necessity for blowing out at short intervals tinuity of conduction, a safety from lateral a part of the boiling water, from their being explosion, especially the conduction of the no incrustation within the boiler to impede electric fluid over the side of the ship, and an the transmission of heat, and from the ne efficient method of shortening the conductor cessity which this system of condensation without injury to its continuity, when the induces, to prevent, as far as possible, any top-gallant and top masts are struck. In waste of steam, as its place must be supplied future I hope therefore, that Mr. Hill will by fresh water produced by distillation from make himself a little acquainted with the salt water.

facts of a case before he arbitrates on the No account can be rendered of the com claims of parties to inventions. parative cost of repairs in these two vessels, There is now no longer any question in consequence of the repairs being performed

amongst persons versed in electrical science, by contract, and of the boilers of the Volcano as to the course taken by electricity through being made of copper ; but considering that conductors; for it has long been settled that the whole of the internal parts of the boilers conduction is in ratio of the mass, not of the of the Meyæra are now perfectly good, surface of a conductor. Neither of the to which, when salt water is used in iron experiments quoted by Mr. Hill prove any. boilers for an equal length of time is never thing to the point, but if he will take two the case, and that the condition of some equal lengths of iron wire of precisely the parts of the engines is certainly better than same diameter, and flatten one of these into if salt water had been used, we think we a thin riband, and then pass equal charges

annum.

through the riband and the round wire, he will find them conducted with equal facility; of course, as Mr. Hill is so well versed in electricity I need not point out methods of proving the amount of conduction through each wire. I have the honour, &c.,

MARTYN ROBERTS.

FIRE-BASKETS.

Sir,—The present fire-baskets are adverse to perfect combustion, to good draught, to steadiness, to warmth, and to facility of mending the fire. A fire-basket should be of thinnish cast iron (thinnish for lightness, but not in too great a degree, for fear of unsteadiness); the backing, and the sides, should have holes in them, like the inner back of most register grates, but much more numerous and smaller, (this ensures perfect com. bustion); the bottom to be grated in like manner and of the same thickness, (for steadiness,) as ordinary grates, and the front to have very slender bars like the present fire-baskets. The dimensions to be as follows : height 6 inches ; width in front, 8 inches ; at back, 5 inches; and the internal depth from front to back 4} inches.

Some of your readers may perhaps manufacture such for the present season.

A CONSTANT READER.

the thing done, if possible, before another three months pass over our heads, or we may be told that the estimated cost will then not exceed 123,8841. A suggestion was made that the services of Mr. Guppy, who officiates as engineer, should be dispensed with, and thereby save 5001. a year ; but I say no ! If we are to finish the ship, let us procure the additional assistance of a real, practical, industrious engineer, in whose ability we may place confidence for the short time we are to remain a company, and that the 3001. or 4001. paid weekly be properly spent, and that the system of making, altering, and re-making, which has been so long practised to our cost, and of advantage to none but our salaried servants, be put an end to. I wish not to be understood as hinting at any incapacity in Mr. Guppy as engineer, seeing that the title and diploma may be had even easier than by setting one's legs under the office table of a C. E. in chief, for a couple of years. If 20,0001. is to be borrowed, let it be done at once ; let the 17,0001. calls be enforced, the ship finished and sold, if possible; wind up the concern, and dismiss the living, as well as dead incumbrances. Judg. ing from past experience, I dread to antici. pate, that the more we spend the more we shall be required to supply.

An attempt was made to comfort us by the prospect of realizing 27811. by the sale of timber and stores, but what the stores are, does not appear. Presuming it to be secondhand timber, sold at a good price, it would require, I am informed, about 55,620 cube feet, equal in bulk to fully one quarter of the bulk of the vessel.

One cannot but think that the people of Bristol, with the exception of two, are perfectly innocent of sleeping with "

one eye open;" to me it appears that they keep both shut.

I am, Sir,
A LUCKLESS SHAREHOLDER.
Bath, November 15, 1842.

THE

GREAT BRITAIN" STEAMER. Sir,-Your publication has given an able description of the “Great Britain” steamship, which has materially assisted to excite great interest in the public mind ; and ima. gining your pages are still open to any observations, whether in approval of the merit (if any) of the management pursued, or in denunciation of the indiscreet expenditure of the company's resources, I beg leave to request a place for a few remarks on these points.

I am one of the unfortunate shareholders, and am now become so sick of the continued demands, and want of money, that I feel almost reckless of the consequences.

In August last, we were told that the cost of the new ship would not exceed 76,1161. ; but at the meeting held at Bristol, on Friday last, just three short months after, we are told that the estimated cost is not to exceed 100,0001.! Surely, this is arithmetical progression with a vengeance, being at the rate of nearly 96,0001. per annum. I respectfully and most feelingly put it to my brother shareholders, whether it is not better, instead of reducing the weekly wages, from 3671. to 3001. as proposed, to increase them, and get

DOMESTIC PUMP.

Sir,-Some time ago, on perusing your useful and instructive Magazine, I noticed with pleasure an account of a small pumping-engine to be fixed on board steamers, in order to relieve the poor stokers from their arduous duties in pumping up the boilers when the engines that work the vessel are not in motion. I beg now to call your at. tention to a new mode of raising water, invented by a Mr. Egeldine, for an equally laudable purpose, namely, the ease and com. fort of the domestic servant. This talented gentleman has lately erected one of the

machines at Mr. Harmer's seat, Ingress Park, of the cock, feed or suction pipe, particu. Greenhithe, which is now in daily use, and larly when more than one length is on, which the performances, I should say, are perfectly admits a portion of air through the seams, satisfactory, though the inventor still thinks joints, &c., yet not sufficient to prevent the he can improve it considerably. One of the engine fetching, or charging itself at first, servants, when I was there, was procuring The consequence is, that on any stoppage of more water with it than I ever saw raised the engine for a short time, to shift the hose, with a pump in the same space of time, and &c., the air so admitted into the feed-pipe certainly with not a quarter the labour of a displaces the water therein, and on the order common pump handle. Much praise is due “Go on," the air must first be extracted to the inventor, for the simplicity of its con and allowed to escape through the main struction, and also for the taste he has dis valves, before the barrels will be charged played in its appearance, which is both light with water, and work. But the main valves and elegant.

are firmly closed by the superior weight of It is to be hoped, that as soon as he has the column of water, instead of being set in secured his patent, he will make this valuable an open position, as Mr. Baddeley says ; and, invention known to the public, who cannot by the motion of the piston up and down, a fail shortly to adopt these machines generally, portion of the air in the feed pipe gets into more especially as the cost is very trifling. the barrels, and is there alternately expanded

Knowing how willing you are to make and condensed, without any discharge of known any new invention, I hope you will water from the branch pipe; the spring or favour me with a corner for this notice at force of the air so condensed not being suffi. your earliest convenience.

cient to open the main valves and escape. Yours, &c. &c.,

To remedy the evil complained of, without A CONSTANT READER. any addition to the engine, all that is neces

sary is, previously to discharging the water on the fire, to pump some water into the cistern of the engine, (which I have fre

quently done,) say till it is half full, and WORKING FIRE-ENGINES.

when the engine becomes affected by the Sir,- In the present volume of the Me vis inertia of the fluid, to turn the handle chanics' Magazine, page 364, your intelli. of the cock a few seconds to feed from the gent correspondent, Mr. Baddeley says, “ In cistern, when the barrels will become charged working fire-engines, under certain circum.

with water. Immediately turn the handle stances, a very striking and somewhat in. back, and the engine will work from the convenient illustration is afforded of the vis feed pipe as usual. I have tried this several inertia of fluids. This happens when the times, and always succeeded. If the feed hose is led to the top of a high building, or pipes, cocks, &c., always continued sound, has by other means a great altitude given to or when working from the cistern, the enit. So long as the engine is worked, and gine would always work after any stoppage, the ascending column of water kept in mo whether fitted with angular yalves or others. tion, the jet is delivered from the branch

Trusting to your kindness for an early pipe in the usual way ; but, should the en insertion of this in your valuable Magazine, gine be stopped for a few minutes, to shift I am, Sir, your obedient servant, the hose, &c., the pressure of the quiescent

AN OLD SUBSCRIBER. column of water cannot be overcome. On

Maidstone, Nov. 10, 1842. beginning again to work the engine, the delivery valves become set in an open position; the engine handles fly freely up and down, as the water passes from one barrel

OPTICAL DELUSION IN RAIN DROPS. to the other, which is the only effect that

Sir,-While under a shower of rain, I can be produced. The vis inertia of the high column of water contained in the ele

have stooped my head to allow the rain to vated hose cannot be thus overcome, but

run from my hat, and thus looking down must be got rid of in another way."

perpendicularly on the drops as they fell, Now, Sir, I do not see what the vis inertia

they appeared to be as black as ink; $0 of fluids has to do with the effect your cor

much so, that at first I thought they were

discoloured from the black 'dye of the hat. respondent complains of; for, in my humble opinion, it arises from quite a different cause ;

The same rain drops, looked at horizontally, and I should think there is scarcely a practi.

while yet hanging to the leaf of the hat, cal fireman but is aware of it, and has a

sparkled like diamonds. remedy at hand. The cause generally ori.

J. N. ginates from the more or less unsound state

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