requiring a donkey-engine to keep the leak under. But the source and anxiety of alarm," says Dr. Scoresby, was the discovery of "weakness and too susceptible working of "some of the plates and angle-irons near the "junction of the stem with the keel. Some "support had been applied within to the upper part of the weak place; but the "apprehension of a risk of forcing off the "plates had hitherto prevented any appliance "to the latter part, where as the external pressure varied as the ship plunged, the working (6 was most considerable. The compartment itself, happily, was but small, and it was "thought to be securely water-tight, having in "the outset of our voyage been filled, as a tank, "with fresh water. But in the case of plates working loose, or, by working, cutting off the "heads of the rivets, as was feared, it was "impossible to calculate on what the effect of 66 66 [NOVEMBER 4, 1859. "tion with reference to sailing vessels; but a become one of great importance. It was time very important consideration of the subject to break out of the antiquated systems of ages, "attaches itself to steam-vessels, and particu- and at least attempt an improvement in this "larly to those fitted with screw propellers. branch of nautical mechanical science, in which "I will, therefore, proceed to point out how there has not been any marked change for up'peculiarly adapted my invention is to steam wards of 200 years. The introduction, there"navigation. It has been shown that the top-fore, of Mr. Cunningham's invention into the "sails can be reefed by few men, and that, too, Royal Navy is a striking event in its history; "without the exercise of any particular nautical and Commander Power's duty of making the "skill. On reflecting on these two very strik- first use of it has been an important one. "ing considerations, viz., that the operation Although we have reason to know that the "which now requires the assistance of the whole principal object which Mr. Cunningham had in crew, and all the nautical ability of the ship, view when he devoted his time and ability to can be accomplished by a fraction of the num- the great work of introducing his invention into ber, and those untrained seamen, the impres- the mercantile marine was the saving of life; "sion cannot fail to be received, that such an still, as the advantages and capabilities of the "invention is peculiarly suitable to screw steam- plan developed themselves, other considerations vessels, and so it is. There cannot be a ques- were suggested, and the expediency of applying tion but that a steam-ship, whether propelled it to ships of war was entertained. We again "by screw or paddle wheel, should be in all quote an extract from Mr. Cunningham's work respects as perfect a machine as possible. The before-mentioned bearing on this point:utmost ability of man has been directed to- "Hitherto I have confined myself to conwards this object, so far as the steam power "sidering the applicability of my invention to "is concerned, but hitherto, although, by the "the mercantile steam navy, but it may further "application of the screw propeller, the steam "be considered how far suitable it is to steam power remains no longer a principal, but the "ships-of-war. In action, the tactics of a war "sail power resumes its ancient importance, "steam-ship would doubtless be to depend on "and the steam may be viewed only as an "the control of the steam-power alone; the auxiliary; still, the bringing of that sail-power" failure, however, of that power by damage to under mechanical control appears to have "the machinery would necessarily oblige her to "been entirely lost sight of. The object which "have recourse to her sails; and the ability to "has occupied the attention of the ablest engi-"apply the sail power with the utmost celerity, " neers for years to accomplish, viz., to bring" and without exposing men aloft, would become "the navigation of a ship as much as possible" an object of the greatest importance. Here, under the control of machinery, is thus over- then, the advantages offered by my invention looked, and the steam-ship is relapsing into "; are very apparent. A steam ship-of-war, the same troublesome machine to navigate "rigged and fitted in the manner before de"that it was 100 years ago, indeed more so, for "scribed, would be enabled to go into action "the immense yards and sails of our large "with her topsails and topgallant sails rolled CUNNINGHAM'S SYSTEM OF REEFING ocean screw ships are disproportionate to the "snugly up on the yard, yet ready for instant SAILS FOR THE ROYAL NAVY. number of seamen comprising their crews; setting, without exposing men aloft. The We have from time to time in this journal al"and hence, in fact, all that has been gained" ability thus afforded would not only give luded to Mr. Cunningham's system for working by the exercise and practice of years of pro- "the ship a superior advantage in the event the square sails of ships, more especially with found mechanical science, ingenuity, and skill," of her machinery becoming disabled, but reference to its extensive use in ships of the "is that sailing ships can be propelled in a "would also enable her to use any of these mercantile marine. It is now with much plea-calm, and otherwise assisted by auxiliary "sails with great facility and effect in assisting sure that we observe its introduction into ships belonging to the Royal Navy. the entire displacement of a plate or plates "in the bow might be, or where the mischief" "might end." It is impossible to read these statements and not see in them an indication of that defectiveness of construction which seems to have manifested itself so fatally in Dulas Bay. The thing most to be apprehended in such cases is, however, inferiority in the iron of which the ship is built. We know that much inferior metal is sold as "ship iron," whereas there is scarcely any work in which excellence of material is more to be desired than in that of shipbuilding. This state of things should be remedied. In the name of Christian charity let us not expose our fellowcreatures to violent deaths, 500 at a time, for the mere difference in the price per ton between good and bad iron! About a year and a half ago Her Majesty's troop-ship Perseverance was fitted at Portsmouth on the "Cunningham system," upon the application of her late commander, John McDonald (who has thus been the means of introducing the system into the Royal Navy); and lately Her Majesty's ship Urgent has been also fitted at the same port upon the pressing request of her spirited commander, W. H. Hire. The first use of the system in Her Majesty's Navy was entrusted to Commander Edward R. Power, of the Perseverance, an old and experienced officer, who, after two voyages to the Mediterranean and one round the Cape of Good Hope in the winter time, has been called to report on the invention. We have been favoured with a perusal of the official report, from which we extract the following very striking passage:" In variable winds and squally "weather, Commander Power was able to make "sail, and relieve the engines, when, with the "ordinary topsails. it would not be judicious "even on account of harassing and exposing the men to continued wet clothing, the efficient "number in the watch of Her Majesty's ship "Perseverance being so small." upon steam-engines; but most gravely must it be 66 66 We must now call attention to the following" extract from a small work published by Mr. Cunningham six years ago, on the sail-power of steam-ships, by which it will be seen that the views which he then held regarding the advantages of his system to screw steam-vessels have been faithfully realized in practice :"Hitherto I have only treated of my inven "in the tactical movements of the ship." for not using the Cunningham system in the We know that a reason given by naval officers Royal Navy is the necessity which there exists for keeping up the old method of working the sails, in order to exercise the crew aloft. This be feared that our seamen are not possessed of no doubt is very desirable, especially as it is to the same agility and skill that some years ago so greatly distinguished them from the seamen of other countries. But still, Mr. Cunningham's brief remarks on the application of his system to ships-of-war deserve serious attention. Steampower has greatly altered the features of naval warfare. We shall no longer have, as a rule, fleets engaging each other under sail, when superior seamanship affords an advantage. Steampower levels all these considerations, and the fleet which possesses the most expert artilleryWhy, then, cling pertinaciously to the contimen will be the most likely to win the battle. that would be well devoted to gunnery instruction. nuance of exercises which occupy valuable time We shall watch the progress of Mr. Cunningham's valuable invention in Her Majesty's navy with much interest; and we trust at least that the equipment of Her Majesty's ships Perseverance and Urgent is the prelude to the fitting of all the troop ships and other shortly-manned vessels in the service. The circumstance that the Cunningham system is now fairly introduced into the Royal There can be no doubt that the question of Navy suggests the expediency of some means improving the mechanical appliances for work-being adopted for the instruction of officers in ing the sails of ships, especially steam-ships, had the use of it. We hear that its operation is as ⚫ We dissent from this. See previous article.-Eds. M. M. simple as can be possibly conceived, and that แ Mr. Cunningham has published copious instruc- which were brickmakers; he also quotes the ment. We understand that there is something remarkable about the fitting of the Urgent. The yards of men-of-war are constructed in a different manner to those of merchant ships. The former are furnished with oak battens of considerable thickness towards the centre of the yard secured by hoops, while the merchant ship yards are without these battens. However, Mr. Cunningham has fully conquered any difficulty that might appear to exist, and the yards of the Urgent are remarkable for their snug appearance. Another peculiarity in men-of-war is, that they reeve their topsail-tyes through blocks upon each side of the topmast, while the tyes of merchant ships are generally led through sheaveholes. Mr. Cunningham has met this by having two neat iron blocks placed well forward on the topmast, which brings the lead of the chains nearly up and down. The advantage of all this has been, that the new system was applied without even the topmasts being sent down; indeed, from the time the iron work arrived from London, the yards and sails were all completed and ready to go aloft in three days. These are important considerations with reference to ships of war, as it shows that they can be very quickly altered to the new system, and without involving any great change aloft. It shows, too, that if need be the sails and yards can be fitted with the reefing gear, and yet still be used on the old plan for purposes of exercise; the reef beckets can be kept on the sails, and the toggles on the yards, and without interfering with the working of Mr. Cunningham's system, provided that the reef earings are unrove before the yard is worked. This is very important. Mr. Cunningham in the work before alluded to points out the ability which his invention affords of sailing ships with fewer regular seamen in their crew. He instances a case where a ship, during the late war with Russia, proceeded to sea with a crew a large proportion of men which composed the crew were necessarily We may have occasion again to say a few Since commencing these remarks, we have received information to the effect that another of Her Majesty's troop ships has been ordered to be fitted by Mr. Cunningham-Her Majesty's ship Vulcan, at Portsmouth, at the request of Commander Strode, who commands her. UNSINKABLE SHIPS. number of the Journal of the Society of Arts. Mr. Atherton's object in the first instance was to make gun-boats, mortar-boats, floatingbatteries, &c., invulnerable; and he asksWhy not make them up to the lines of their load displacements "solid masses" of material, of such specific gravity that they shall not sink however much they may be perforated by shot? He considered that a solid combination might be made of cork shavings, light wood sawdust, rush stems, cotton waste, flock, hemp, and other light material, by the aid of a solution of gutta-percha, or other chemical substance. This mass might be made, he thought, so tough that it could not be knocked to pieces by shot, and so light that it would be only one-half the specific gravity of water, and therefore unsinkable, however perforated by shot, and also capable of carrying an armament and naval equipment to the extent of nearly one-half the weight of its own displacement in tons. "Such vessels of light draught accompanying fleets of war as "tenders to line-of-battle ships, whence they "might be manned and stored as occasion might require, would, I submit," said he, "form a useful auxiliary available for shore service, or for attacking land batteries, which deep draught ships of the line cannot ap"proach, and would be sunk if they could." The idea was first broached by him two years before as being applicable to the construction of vessels for carrying treasure. 66 66 In the interval that elapsed between the dates of Mr. Atherton's letters his ideas appear to have expanded enormously. We no longer hear of unsinkable "tenders to line-of battle ships" only; but ships of war of all classes are to be constructed on the unsinkable principle. "I have no doubt," says Mr. Atherton "that at a moderate cost per ton of shipping, existing vessels may be rendered unsinkable, "and that a new modification of ships of war of all classes may be devised, such as may obviate "the horrors which appear to be otherwise "inevitable in maritime warfare under the fire " of modern ordnance." It ought to be stated that Mr. Atherton's reason for renewing his proposition at the present time, and in its enlarged form, is a belief of his (founded on a paragraph in the Times) to the effect that ironcased ships will be incapable of resisting the fire of modern ordnance, and that, as recent events have shown, ships of the ordinary build may be sunk by the fire" even of an extempo"rised Chinese fort." There is, of course, one great primary obstacle to the carrying out of Mr. Atherton's plan, namely, that no such material as he requires for his purpose is at present known. The singular compound mentioned in his first letter does not seem to satisfy him now, and he therefore proposes that £250 be subscribed and placed at the disposal of the Council of the Society of Arts, to be awarded in premiums of £150 and £100, "for the discovery and specifi"cation of the materials and process of manu facture most available for producing a com"bination of materials constituting a solidifying "pulp possessing in the highest degree the properties of specific lightness, toughness, nonabsorption of water, and cheapness, or a "metallic cellular body having the same pro"perties." But how a "metallic cellular body" is to answer the purpose we cannot conceive. It seems to us a very remarkable circumstance that Mr. Atherton loses sight altogether of the danger of fire, which is more likely to do injury than anything else now that the use of shells is universal in naval warfare. His light buoyant material must be presumed to be exposed to the fire of ordnance, for its whole merit is to consist in being unsinkable when "perforated" 66 engineering firms in and out of London. But in this instance no such course has been adopted. "Kissing" has been said to "go by "favour," and so far as that pleasant operation is concerned the saying is doubless just; but why the privilege of coining the monies of the State is to be subject to the same rule it is not easy to see. Perhaps in the course of two or three months, and when Parliament is sitting, some Member of the Government may enlighten us on the point. by shot or shell; and, consequently, unless it the mode to be adopted in the realisation of the were uninflammable as well as unsinkable it great reform. There is no manner of doubt that would be of little use. Mere "lightness, the establishment for making the national monies "toughness, non-absorption of water, and cheap--the Royal Mint-might, with an amount of ness" alone will not therefore do. If we are outlay upon new mechanical appliances and wrong in this we shall be glad if Mr. Atherton fitments inconsiderable in comparison with will show us where our error lies; but he must the advantages to be derived therefrom, be not forget that “liquid fire" is as veritable a made quite equal to the task of which ministers means of offence as the Armstrong gun, and have assumed the responsibility. The four or has proved its efficacy quite as decidedly. Of five hundred tons of bronze coins which would course we are quite aware that a solid substance have to be pressed into being before the old would not be set fire to by the mere lodgment copper could be entirely superseded would, At present, the fact that the initiation of a of a red-hot shot in it, with no other access for with little expense, in the course of lers than new coinage on a vastly improved plan, and air save the hole by which the shot entered. three years, and without any interference with which is destined to form an era in the minting But the explosion of powerful shells within such the production of gold and silver coins, be annals of the country, is to be taken out of the a substance would be a very different matter, struck on Tower Hill. Why, we ask--and the guardianship of Her Majesty's coiners and put and would, we think, in most cases have the public no doubt will reiterate the question into those of a company of Birmingham coneffect of setting it on fire. There can be no why are we to have a contractor in Birming- tractors, is the one to which we have felt it great harm in offering the premiums proposed "ham employed to do the Mint's work?" proper to direct public attention, and in by Mr. Atherton if there is the least chance of obtaining a very light fire-proof and water-ble. There is no sort of manufacture conducted To us such an arrangement seems inexplica- omitting to do which we should have omitted our own duty. We publish on another page a proof solid material, because such a material by Government which requires in all respects copy of the paragraph named, and have merely would be useful for many purposes; we have so much caution and care as that of money, and to say that the Manchester Guardian has been no desire, therefore, to obstruct the action of no manufacture, therefore, which should be totally misinformed in regard to the fact that the Society of Arts in this matter. reservations. But here, without any shadow of years." We are in a position to assert that more jealously hedged in by restrictions and the firm referred to therein have "executed the (6 copper coinage for this country for many good, pecuniary or otherwise, the carrying out of a great reform in the coinage is, to be enthey have done no such thing. The Parliatrusted to hands whose interest is not to pro-mentary returns will demonstrate the fact that duce pieces of money so perfect as to defy the from 1805-6, when the last coinage of copper cunning labour of the counterfeiter, but such as took place at Soho, up to 1852, and from 1855 shall return the greatest amount of profit to Britain and her Colonies have been executed to 1859, the whole of the copper coins for Great themselves. Surely the Chancellor of the Exchequer has not thought sufficiently upon the exclusively at the existing Mint on Tower Hill. subject, or he would not have sanctioned so If the other statements of the paragraph were gratuitously dangerous a proceeding. We say tion of copper coin, why, it might be treated as inaccurate as this with regard to the produc"have sanctioned" it, because from the terms of the paragraph in question it appears that with silence; but there is, as we have said, sanction has positively been given to it. Let truth in the averment that new engines and not the singularly favoured and fortunate firm new coining presses are being prepared for in Birmingham who have obtained, without Birmingham contractors, and we allow the paracompetition, at least the promise of being engraph to speak for itself. trusted with the highly important duty of supplanting the worn-out copper with the new mixed metal coins, imagine that our remarks as to the profits to be made by the transaction WHAT is to be done in the matter of the Great are at all personal. That would be a great Seal Patent Office Library? Over and over error; our criticisms are based on the laws again the manifest want of increased accommowhich govern contractors in general, and not dation, not only for the readers who frequent themselves in particular. They may, for aught it, but even for the very books, has been pointed we know to the contrary, be quite as disposed out by the London press, from the Times downto make themselves worthy of the great occa-wards, and yet nothing has hitherto been done. sion as any other firm in the kingdom, but they are subject to the commercial law which bids them "make as much out of the job" as they can. It matters not to us whether it be Messrs. A, B, C, or H, who undertake the task, we say it is not one for contract at all, and that the Government is in error in making it one. But we do not understand why (admitting for a moment that the Institution which we have, and which is kept up at a cost of some thirty odd thousand pounds per annum, is incompetent to the task), specifications should not be put forth to all and sundry engineers, button-makers, breastplate-makers, stampers of gas-fittings, &c., so as to give them also an opportunity of competing for the coinage. That would appear COINING BY CONTRACT. to be a course so completely in order-when Ir is not without an intense feeling of dissatis- once the question of contract or no contract is faction that we have observed a paragraph answered affirmatively-that it is impossible to "going the round" of the newspapers intimat- understand why it has not been done ing, in terms too positive and plain to be mis- in this instance. When it was proposed understood, that the Government intend putting by Sir John Herschel, at the commencethe coinage of the new mixed metal monies ment of his mastership in 1852, to hand out to contract. Our readers are well aware over the entire plant of the Mint to contractors, that the proposition for re-organising the in- who were to be bound under heavy penalties to ferior coinage of England was first promul- produce coin of proper weight, standard, and gated at the commencement of the present finish, and to be always under the control of year-in the pages of the MECHANICS' MAGA- officers of the establishment appointed by the ZINE, and since that is the fact we naturally Treasury, the opportunity of undertaking the assume to ourselves the right of comment upon contract was offered to the most eminent But, having said this, it remains for us to say further that even if such a material as we have spoken of should be produced, and placed in Mr. Atherton's hands, we should be disposed to ask wonderingly -- What will he do with it? and we think the Society of Arts should consider this question before they accept his advice respecting the premiums. With a ship solid below the water-line where would he place the engines, coals, provisions, powder, and all those other stores which now are stowed in the lower parts of the ship? We know not how to conceive a plausible answer even to this question. Will Mr. Atherton kindly help us out of the difficulty? We hope he will, if possible, for his own credit's sake. It is easy enough for any man to make propositions in the form in which the present one comes before us; but it will not do for a gentleman who has taken a wrangler's degree at Cambridge, and made himself prominent in scientific discussions, to leave his propositions utterly undeveloped. It is, we think, incumbent upon Mr. Atherton to show us what the "new modification" of ships of war is to consist in, assuming that the material which he asks for is supplied. We should be heartily delighted to find that he has the design of the unsinkable war-ship in his mind. This, in our judgment, would be worth a very handsome "premnium," and the Society of Arts would perhaps do well to offer one for it before they offer the others. They need not fear any very extensive competition. Of course it is quite possible to build enormous rafts, and call them by the new name of "unsinkable ships"; but these can hardly be what Mr. Atherton is thinking of, since he talks of rendering "exist"ing vessels unsinkable, and since he must know perfectly well that the time for abandoning real ships has not yet arrived. What, then, is he thinking of! We respectfully invite him to tell us. THE GREAT SEAL PATENT OFFICE At the present moment the wretched passage For it is perfectly manifest that a public library in connection with the Patent Office has become indispensable. It is the only simple means which can be afforded to inventors for enabling them to act justly to themselves and honestly to each other. There must be a place | ence to them, especially as a company designed | bear any required amount of strain without the 66 in which they can make reference to the speci- 66 THE FOUNDER OF MECHANICS' MR. CARLYLE tells us, and we all of course We appeal, therefore, to Mr. Edmunds. We are tired of appealing to Sir Richard Bethell, Sir Henry Keating, and their colleagues, although they really ought to support us cordially in this matter. Sir John Romilly, above all, being the only permanent Commissioner, ought to do his best for us. But Mr. Edmunds is the executive officer. We turn to him in this emergency, and we shall continue to look to him until something is done. We shall not cease to urge our claims upon his attention until our legitimate and press-forwarded to various parts of the world. Tele-author of them. "We seconded him, and no more. ing demands are complied with. SUBMARINE TELEGRAPH CABLES. By at Newcastle-on-Tyne that old and dismal error Lord Brougham has this week been repeating tions. George Birkbeck, he again says, was the of his about the founding of mechanics' institu "We laboured as hard as we could, but he be- 66 graph companies are therefore assured that the cables manufactured by them will not be destroyed either by the process of paying out or Ir is useless to conceal the fact that submarine by lying in the holds of ships while proceedinggow, where he delivered a course of lectures to electric telegraph cables, as hitherto constructed, to hot climates. "The method of applying the have been to a very great extent failures. There"india-rubber according to the patent of institutions. He then transferred it to London working men. This was the origin of mechanics' is great reason to doubt whether their insula- "Messrs. Wells and Hall, admits of no defects "for the sake of greater extension, and as being a tion has ever been perfect even when they have "in construction, but insures a certainty of left the manufactories; in many instances they "electrical integrity which is altogether unexmore important place for large support. He it have been greatly injured in transport from the "ampled." This is the language of the patenwas that propounded it in London also, and not works to their destinations; they have very tees themselves, and will therefore, of course, only proposed it and furthered is, but spent frequently sustained great damage in the pay-be of little value of itself; but we must admit "have never been repaid. These were the services "large sums of money upon it, which his family ing-out process; and, finally, they have been they have grounds for their statement. far too susceptible to injury even after submer-winding on successive ribands of the pure gence. All these things, of course, entail great rubber, the whole process of manufacture can expense and loss upon the proprietors of the be watched at every stage, and it is difficult to cables who are generally the shareholders of see how any sort of defect can occur; while, by companies and it is not at all surprising that laying the successive ribands on partially over effectual remedies have been sought. each other, and in opposite directions, even if a defect should occur in one fold it would be effectually neutralized by the next. These suecessive layers of india-rubber being again covered by a close-laid elastic cord, become so pressed and amalgamated as to form one person's claim to be the founder by pushing the fectly sound and impervious insulator. With these facts before them, some persons have leaped to the conclusion that gutta-percha, which has been used as the insulating material in most of these failing cases, is not a suitable material for the purpose; but we are by no means prepared to go this length with them, because we know that much of the mischief has The external coverings of the cables thus arisen from causes not at all assignable to the insulated may be of various descriptionsintrinsic qualities of the insulator. At the same either all of wire or in part wire, or in part a time, whatever there may be to say in favour mixed covering of prepared hemp and wire, as of gutta-percha, it appears beyond question that may be desired. The coverings hitherto pure india-rubber is, to say the least, in all re-adopted have usually been made upon the spects equal to it in this respect. Pure indiarubber properly applied is, in fact, a perfect insulator. Its proper application is, however, a matter of immense importance. How, then, may this be effected? We honestly confess that we know of no method by which this is to be done with the same certainty of a good result as is secured by the system lately introduced by Messrs. Wells and Hall. We have, on a former occasion, directed attention to their plans; but, as we have lately had occasion to inspect the machinery completed for them by Messrs. Easton and Amos, we think it desirable to repeat our refer spiral principle. The consequence is, they have 66 of Dr. Birkbeck, and he it is that we must call "institures. He laboured, we seconded him, no "and always treat as the founder of mechanics' "capacities. We were his fellow-labourers, but he “doubt, according to our means in our different was the first and the originator of this great step in social progress." 66 « These are Lord Brougham's present statements. He is not insensible to our late strictures, for, in the words which we have put in italics first, he endeavours to avoid Mr. Robert origin of mechanics' institutions back to the time of the Glasgow lectures to working men. In the second italicised sentence, however, he makes the distinct assertion that Dr. Birkbeck first propounded the London Mechanics' Institution. The assertion is false-distinctly, unquestionably, demonstrably false! We have before shown why it is so; will Lord Brougham attempt to show the contrary? Assertion, even from him, and, although repeated a thousand times, is not proof. Mechanics' institutions sprung from the MECHANICS' MAGAZINE, and originated in the brains of its first editors, Mr. Robertson and Mr. Hodgskin. If there were no taint in Lord Brougham's noble nature he would say the same. ON THE TRANSMISSION OF HEAT OF Nature in the following way: a source of heat, Some analogies between sound and light were first pointed out: a spectrum from the electric light was thrown upon a screen-the spectrum was to the eye what an orchestra was to the earthe different colours were analogous to notes of different pitch. But beyond the visible spectrum in both directions there were rays which excited no impression of light. Those at the red end excited heat, and the reason why they failed to excite light probably was that they never reached the retina at all. This followed from the experiments of Brücke and Knoblauch. These obscure rays had been discovered by Sir Wm. Herschel, and the speaker demonstrated their existence by placing a thermo-electric pile near to the red end of the spectrum, but still outside of it. The needle of a large galvanometer connected with the pile was deflected, and came to rest in a position about 45 degrees from zero. A glass cell, containing the transparent vitreous humour of the eye of an ox, was now placed in the path of the rays: the light of the spectrum was not percepti bly diminished, but the needle of the galvanometer fell to zero, thus proving that the obscure rays of the spectrum, to which the galvanometric deflection was due, were wholly absorbed by the humours of the eye. having a temperature of about 300° C., was placed The same method was applied with other gases, and with most remarkable results. Gases differ probably as much among themselves with regard to their action upon radiant heat as liquids and solids do. Some gases bear the same relation to others that alum does to rock-salt. The speaker compared the action of perfectly transparent coalgas with perfectly transparent atmospheric air. To render the effect visible to the audience, a large plano-convex lens was fixed between two upright stands at a certain height above a delicate Reference was made to the excellent researches galvanometer. The dial of the instrument was of Melloni. In a simple and ingenious manner he illuminated by a sheaf of rays from an electric had proved the law of inverse squares to be true lamp, the sheaf being sent through a solution of of radiant heat passing through air, and the emi-alum to sift it of its heat, and thus avoid the fornent Italian inferred from his experiments that mation of air-currents within the glass shade of for a distance of 18 or 20 feet the action of air the instrument. Above the lens was placed a upon radiant heat was totally inappreciable. looking-glass, so inclined that the magnified image This is the only experimental result now known of the dial was thrown upon a screen, where the regarding the transmission of radiant heat from movements of the needle could be distinctly ob. terrestrial sources through air; with regard to its served by the whole audience. transmission through other gases it was believed amined, the currents from the two piles being that we were without any information. equilibrated in the manner described; the tube was exhausted, and a small but perfectly sensible deflection was the result. It was next arranged that the current from the pile at the end of the tube predominated greatly over its antagonist. Dry coal-gas was now admitted into the tube, and its action upon the radiant heat was so energetic, the quantity of heat which it cut off was so great, that the needle of the galvanometer was seen to move from about 80° on one side of zero to 80° on the other. On exhausting the tube the radiant heat passed copiously through it, and the needle returned to its first position. It was, however, very desirable to examine the action of such media-desirable on purely scientific grounds, and also on account of certain speculations which had been based upon the supposed deportment of the atmosphere as regards radiant heat. These speculations were originated by Fourier, but it was to M. Pouillet's celebrated Memoir, and the recent excellent paper of Mr. Hopkins, to which we were indebted for their chief development. It was supposed that the rays from the sun and fixed stars could reach the earth through the atmosphere more easily than the rays emanating from the earth could get back into space. This view required experimental verification, and the more so, as the only experiment we possessed was the negative one of Melloni, to which reference has been already made. Air was first ex Similar differences have also been established in the case of vapours. As representatives of this diverse action, the vapour of ether and of bisulphide of carbon may be taken. For equal volumes, the quantity of heat intercepted by the former is enormously greater than that intercepted by the latter. The energetic action of the solid and liquid compounds into which the element hydrogen enters, suggested the thought that hydrogen gas To test the influence of quality, the following might act more powerfully than air, and the fol- experiment was devised. A powerful lime light lowing means were devised to test this idea. A was placed at one end of the tube, and the rays tube was constructed, having its ends stopped air- from it, concentrated by a convex lens, were tight by polished plates of rock-salt held between sent through the tube, having previously been suitable washers, which salt is known to be trans-caused to pass through a thin layer of pure water. parent to heat of all kinds; the tube could be attached to an air-pump and exhausted, and any required gas or vapour could be admitted into it. A thermo-electric pile being placed at one end of the tube, and a source of heat at the other, the needle of an extremely sensitive galvanometer connected with the pile was deflected. After it had come to rest, the air was pumped from the tube, and the needle was carefully observed to see whether the removal of the air had any influence on the transmission of the heat. No such influ ence showed itself-the needle remained perfectly steady. A similar result was obtained when by drogen gas was used instead of air. Thus foiled, the speaker put his questions to The heat of the luminous beam excited a thermo- The bearing of this experiment upon the action the galvanometric deflection which it produces; its The quantity of heat is measured by the amount of the lime light, the power of crossing an atmo. sphere; but, when the heat is absorbed by the planet, it is so changed in quality that the rays emanating from the planet cannot get with the same freedom back into space. Thus the atmosphere admits of the entrance of the solar heat, but checks its exit; and the result is a tendency to accumulate heat at the surface of the planet. In the admirable paper of M. Pouillet already referred to, this action is regarded as the cause of the lower atmospheric strata being warmer than the higher ones; and Mr. Hopkins has shown the possible influence of such atmospheres upon the life of a planet situated at a great distance from the sun. We have hitherto confined our attention to solar heat; but were the sun abolished, and did stellar heat alone remain, it is possible that an atmosphere which permits advance and cuts off retreat, might eventually cause such an accumulation of small savings as to render a planet withdrawn entirely from the influence of the sun a warm dwelling-place. But whatever be the fate of the speculation, the experimental fact abides-that gases absorb radiant heat of different qualities in different degrees; and the action of the atmosphere is merely a particular case of the inquiry in which the speaker was at present engaged.* THE GREAT EASTERN AND STEAM-SHIP 66 does not do TO THE EDITORS OF THE MECHANICS' MAGAZINE." : Table No. 1, showing the SUPERIOR CAPABILITY of large ships as indicated by a progressively increasing rate of speed corresponding to a progressively increasing size of ship, the ratio cf displacement to power being constant. Table No. 2, showing the SUPERIOR CAPABILITY of large ships as indicated by the progressively reduced ratio of power to displacement corresponding to a progressively increased size of ship, the speed being constant. Table No. 3, showing the SUPERIOR CAPABILITY of large ships as indicated by the progressively increasing distance capable of being steamed without recoaling at a given speed, and with a given per-centage of the displacement appiopriated to cargo. Table No. 4, showing the SUPERIOR CAPABILITY of large ships as indicated by the reduced consumption of fuel per ton of cargo at which goods will be conveyed a given distance, without recoaling, at a given speed. Table No. 5, showing how soon the admitted advantages which result from increased size become neutralised if on the strength of increased size alone, we undertake OBLIGATIONS which involve, on the part of the large ship, an increased rate of speed combined with an increased distance without recoaling. The investigations above referred to, as com While correcting the proof of this abstract, I learned that Dr. Franz had arrived at the conclusion that an absorp tion of 3:54 per cent. of the heat passing through a column of air 90 centimeters long takes place for coloured gases he finds the absorption greater; but all colourless gases he assumes show no marked divergence from the atmosphere. -Poggendorff's Annalen, xciv. p. 337. |
