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201 the pressure, and inversely as the dia speed in the former case was 3} leagues

meter of the wheels. 2. The wear of the road is greater in The remainder of the memoir is occu

proportion as the wheels are smaller. pied with experiments on the shock and 3. On roads of compressible materials, as resilience of elastic bodies, and is not so

earth, sand, gravel, &c., the wear and important. The difficulties of this subthe resistance to rolling decrease in ject, as an experimental one, are very proportion as the breadth of the wheel

great; and perhaps results taken from tires is increased, and with all carriages the actual working of certain suitable and is independent of the velocity.

defined lines of road for a long period, 4. On paved roads, or ordinary stoned arrangements being made for the pur

roads, (en empierrement,) the resist pose, would be more likely to give corance is nearly independent of the rect information than any experiments breadth of the tire, within certain made in the manner of M. Morin. limits, and increases with, and is pro

Water-proof Cloth. portional to, the velocity. The aug M. Menotti's invention of a soap in mentation is less as the carriage is bet solution, for the purpose of rendering ier bung (i.e.on springs) and the road cloths water-proof without stopping their more firm. At slow speeds, the re pores to air, &c., was reported on favoursistance is the same for springed and ably by a commission of the Academy, in unspringed carriages.

January, 1840, and the subject has been These are results of M. Morin's first again brought by him before this body. memoir, some of which, it may be ob This invention of Menotti's is nearly, if served, do not agree with those admitted not quite identical with that patented by amongst British engineers. The second Raper in this country, and both are alike memnoir contains his results as to the re useless. It is quite true that either of lation between the form of wheel and wear these plans, (if they differ,) or any one on the road. The mode of experiment of many others of long anterior date, will adopted was that proposed by M. Navier, enable cloth to resist water gently poured viz., the causing the same load to pass over it, but a very little rubbing or sopping repeatedly over the same track of road, of the cloth sends it through the fabric; and observing the depression. This me so that, although a coat might bear a thod was proposed by Navier in an able shower, say on the shoulders, it would work published by him in 1835, and little wet through under the arms, &c., in a known to Englishmen, entitled “Consi short time. derations on the Principles of the Police The principle of all the methods conof Wheel Carriages.'

sists in fixing in the pores of the cloth M. Morin's principal results in this either an oily matter, by decomposition Report are

of a soap, or an extremely divided pow1. With equal loads, narrow tires degrade der, having little or no affinity for mois

roads more than wide ones; but with ture. As yet, no water-proof cloth exists loads of 5,500 kilograms, and tires of but that made so by India-rubber, or at 0-12 metres wide, the advantage of least, none that will remain so. width is a maximum, and beyond this

Manna. there seems to be no use in augment A substance has recently been introing the width.

duced into commerce as manna, in France, 2. Another set of experiments indicate but which does not possess all the pro

that, with loads proportional to the perties for which that drug is valued. It width of the tires, the widest tircs in is questionable whether the new substance jure the road most.

is an artificial or natural product; and it 3. With equal loads and widths of tire, has been examined chemically by Pelouze,

greatest injury results from the smallest and optically by M. Biot, by means of wheel.

polarized light, according to his own pe4. The same load carried in two two culiar method. wheeled carts produces less injury than

Mannite, the peculiar proximate prinin one four-wheeled wagon.

ciple to which manna (which is a secre5. A springed wagon, at a trot pace, tion from certain trees of the genus Frarproduces as little injury as

inus) owes its efficacy, has scarcely any springed one at a walking pace. The estatory power on the polarized ray. The



solution of manna, however, like that of It requires a bar of iron to be nearly dextrine, or starch modified by the action white-hot, before it will ignite an exof acids, causes the ray to deviate to the plosive mixture of gases. A more likely right of the observer, which arises from source for the air would be, apparently, its containing a quantity of fermentable that it is introduced into the boiler in sugar. This renders the optical examina- combination with the feed-water, and tion of this new sort of manna not quite there evolved on its being heated. decisive, as its effects on light are similar. Some curious examples of explosion This substance consists nearly wholly of are cited by M. Jobard ; among others, fermentable sugar, very analogous to that one of a boiler at Ghent, which was blown produced by the action of acids on starch; up while the man-lid was off, and the and although it cannot be pronounced cer boiler about to be cleaned out. On the tain, it seems not improbable that this whole, as there is no doubt whatever that new sort of manna is, in fact, so made. iron, aided by high pressure, (as, for inThe Galvanometer.

stance, Perkins's Hot Water Apparatus,) M. Melloni has communicated to the will decompose water at temperatures Academy of Sciences a new method of even below ignition, it is quite possible varying at will the sensibility of his gal. that some explosions of boilers may have vanometer, and, when desirable, greatly been due to this peculiar, but certainly increasing its power of ineasuring minute most unlikely, combination of circumelectrical charges, and, by their means, stances; while there can be equally little minute changes of temperature.

The doubt that the vast majority have arisen paper is too long for extraction in an in from simple pressure of surcharged steam, telligible form, but will be read by elec a cause, however, which, M. Jobard will tricians with great interest.

not admit under any circumstances; for Causes of Explosion in Steam-boilers. he says, a boiler gradually overpowered

The formation of explosive mixtures by steam pressure rends at the joints, of gas by decomposition of water in iron which first open, and give vent to water boilers, when in contact with red-hot and steam. A complete treatise upon the plates, has been repeatedly urged as a causes of boiler explosions is yet a desicause of explosion; and as repeatedly has deratum : every author hitherto has had it been shown that, although possibly some favourite crotchet to support, behydrogen might be thus produced, an sides the main point of the matter. explosive mixture could not, as the оху : The Artesian Well of Grenelle. gen is not set free, but taken up by the In a letter to M. Arago, Mr. Combes iron while it oxidizes. M. Jobard, Di. gives his opinion as to the causes of the rector of the Museum of Manufactures singular fattening of the copper tube at Brussels, has published a paper, in lately put down into the bore by M. Muwhich he reasserts this to be a true cause lot, and which has caused so much trouble of explosion, and gets over the difficulty as to get up again. It is pretty generally to oxygen by saying that atmospheric air known already, that, after more than 600 takes its place; that, in fact, water can feet of the copper tube intended to line not be decomposed unless the water be the well had been got down, without any low in the boiler, which cannot happen accident, suddenly, in one night, above unless the feed-pump be out of order, 300 feet in length of the tube became that is, not pumping water, but pumping compressed together flat, and twisted in air into the boiler.

various directions, grasping and retaining He explains, then, the ignition of the a spoon which had been before lowered inflammable compound to arise either down into it. The following is the theory from the contact of the red-hot plates, or of the phenomenon given by Mr. C. The from an electric spark produced by open inside of the jumper-hole had been preing the safety-valve, and the steam rush. viously lined with sheet-iron, at intervals

, ing out.

to support its sides. The water of the It is now well known that a discharge upper chalk continued to discharge large of steam is accompanied with a powerful volumes of sand, which are supposed to disturbance of electrical equilibrium; but have filled up and got wedged between it is not so evident how this is to produce the two tubes, and so stopped up all a spark, in such circumstances as to ignite egress to the water in that way. As the supposed issuing volume of gases. long as the water stood at the same level

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203 inside and outside the tube, the pres that he had no grounds for stating that sures would balance each other, and no his conviction of the supposed injurious injury could result; but the water from effects of my mode of admitting air to the bottom of the chalk would carry up a furnace was, “forced upon him by a great quantities of solid matter also, and be careful and unprejudiced examination of subject to frequent stoppages, obviously several furnaces constructed by Mr. Wil. caused by breakings-down, or wedging liams himself.”. His now triumphant of particles in motion in its subterranean answer is, that indeed he had seen one ducts. Mr. C. supposes, then, that the flow which was erected by the late firm of of water in the inner tube was arrested; Brocklehurst and Company, and which, that the level of the water in it fell, tem after a hasty examination, he ridiporarily, much below that due to the culed as a mere “ peep-show affair," pressure on the outside of the tube; that the (see Mec Mag., April 17). Now, this water of the upper chalk was then corked statement alone, so different in substance up between the tube and the sides of the from his “long attention, and careful well; and that at this moment the sides examination of several"-is a sufficient of the copper tube were crushed inwards. refutation. But as to this one furnace

The portion of the tube crushed was to which he refers, I have to state,-1st. from about 300 feet from the surface to it was not constructed by me, and in seabout 600 feet lower.

veral respects differed from my instrucNew Application of the Electrotype. tions; 2od, it nevertheless was success

M. Peyré, of Versailles, has proposed ful in its operations; and 3rd, it never an application of the electrotype process caused any injury-its internal action which seems likely to be of value, viz., completely negatived the expanding and to the multiplication of accurate graduated contracting, heating and cooling process instruments. It is obvious that, if one and it ever continued to work satisfactoperfect graduated scale of metal can be rily. Thus, if the report was in any way had, without injury, we may electrotype influenced by the action of that furnace, others on it, and others off them, ad in it should have been the reverse of what finitum. The costliness and rarity of it was. The object, however, was to good graduation is well known to those throw discredit, in the garb of a matterwho are at all concerned with instru of-fact report, on my principle of admitments of precision. As a proof of the ting air to furnaces. I am sorry here to power of the process, very ample details have it to say, this is no solitary instance of which M. Peyré gives, he states that a of a prejudging determination to conDaguerreotype plate, having a faint image demn, without enquiry, and on the part of the Christ of Michael Angelo, gave of those whose real interests would sughim copies in copper, in which the design gest the most rigid impartial examination. was as apparent as in the original. But the main allegation in Mr. A.'s let.

ter is, that I threw
the responsibility

of the action of my furnace, in the case of Messrs.

Hamnett's boiler, on my agents. This, MR. WILLIAMS's SMOKBLESS FURNACE

Sir, is the very reverse of the fact; for,

as it was important to me to disprove Sir, -As Mr. Armstrong continues to Mr. A.'s statement, that my plan of adrepeat his unwarrantable statements, I mitting air was, and “ever would conmust beg permission to make a short reply. tinue" to be injurious, I adopted the He now attempts to neutralize the effect most decided measures on that head. I of his admission that his report was wrote several times to Mr. J. Woodiwiss “ founded on erroneous data.” The only (the acting partner) on this subject : and answer I shall make is, that I have the the following extracts from my letters fullest confidence in the statements made will set this matter right :by che solicitor, a wholly disinterested My letter of the 15th of December party. It is quite true, the letter of recanta- last, states, “ I will, at my own expense, tion was not written by Mr. A. himself. I put the furnace in operation for any given never said it was : and your explanation, number of days, which may be deemed in the note attached to Mr. A.'s letter, advisable for testing the value of my renders any further observation on this system, and of proving to your entire sapoint unnecessary. My assertion was, tisfaction, that it is absolutely impossible



to injure a boiler by any operation of my at once had objected to, as defeating my system, so long as it is preserved in a principle; seeing, that by the action of proper state of cleanliness and with a Stanley's feeders, too thin a fire is maindue supply of water. The only condition tained on the bars, and so large a quantity of I shall require is, that a water gauge be air is drawn in from the front as effectually placed on the boiler, and by which the to obstruct the action of the air introfireman can ascertain whether there is a duced in the proper place—from behind. sufficiency of water in it: and further, Mr. A., very naively observes, that that until you are satisfied as to the safe his statements have been “ verified to working of the plan, I be allowed to the satisfaction of every one who has have a confidential person to prevent any chosen to enquire of the proprietors of neglect,” (I might have said—or foul the boiler in question." No doubt of it. play,) “as touching the supply of water. But what say those who have enquired I will give you any guarantee as to the of other, and disinterested, and unsafety of the boiler. This, I think, will prejudiced persons ? Have they enbe admitted to be the experimentum quired of the respectable makers of the crucis : for, had I failed, and had Mr. boiler? Have they enquired of those A.'s theory been correct, the question

who have boilers in action on precisely would have been at once and for ever the same principlethe Liverpool Water settled, and to my discomfiture. Mr. Works Company, for instance ? For, if Woodiwiss should at once have accepted the theory be correct, it must produce the proposal, and Mr. Armstrong have similar effects under similar circumadvised it, as the best test to which his stances. theory could have been subjected, and Now, there is a very important and the surest annihilation of mine, if erro useful consideration arising out of this

But this offer, to take on myself discussion, and which, otherwise, would the risk and responsibility, was declined, be very unsuitably placed in your scienand uncourteously so. This was at least tific Magazine. I allude to the adoption suspicious.

of means for judging correctly, how far In my letter of the 27th of December, any system of combustion, or “ smoke I said " I repeat my proposal to re burning," or arrangement of furnaces, open the air-pipe, and show you that no may be effective or otherwise ; and which possible injury could be sustained by the would enable the owners—the really inadmission of air, as alleged by Mr. A." terested parties—to judge for themselves, Again—" I undertake to make this ap- independently of the theoretical views and plication without auy expense to you imaginary statements of patentees. As without any charge for patent right, and this is a matter of great practical value, with a guarantee against any, and all I propose, (though out of the course I injury, from such admission of air." I had determined on,) in my next commu. trust, Sir, this will be a sufficient answer nication, to go into the question, and to the allegation that I threw the respon

show its absolute necessity. sibility on others. Suspecting, however, I am, Sir, yours, &c. that there was some understanding be

C. W. WILLIAMS. tween the parties, I brought this to the Liverpool, March 7, 1842. test, by adding, If you refuse me, the Erratum.-In my last communication, page 187, world will say you have consented to the

line 19, for, "from 46°, to 4760," read “ from 400 to erroneous statement, and are, in fact, supporting Mr. Armstrong in his unjustifiable attempt to injure me.” My Jast letter to Mr. Woodiwiss states that his refusal was perfectly satisfactory, and the public would know how to ap Sir, I have just perused your extract preciate it. Mr. A. states, that I was from the Bristol Magazine in your numpresent, and a “witness of its failure."

ber for January 1st, respecting the steam I was present, and, on the contrary, navigation of the Atlantic, and the rival witnessed its success. The alteration lines of Bristol and Liverpool; and alwas one suggested by Mr. W. himself, though I think with you that it is true namely, the stopping the action of “in the main,” yet still it contains much Stanley's feeding apparatus, and which I exaggeration, and many of the facts have






been greatly distorted for the purpose of boats have to contend with the severer serving " local interests.”

weather, which is generally experienced 1. With respect to the conveyance of so far to the northward. As to the rethe North American mails :- the Editor marks respecting the punctuality of the of the Bristol Magazine would seem to Caledonia, Columbia, &c., their deteninsinuate that the government had made tion when they have been detained has a “ patronage job of it to serve their always been satisfactorily accounted for, own interests, and that they had abso either from having experienced severe lutely thrown away 35,0001. of the public weather, which, as I have before obmoney. Now, the facts are these : the served, is not so often felt, and never so government having determined on carry; severely on the voyage from New York, ing the N. A. mails by steam, pitched ai on that from Halifax, having met with upon Liverpool as the best port in the icebergs, which is frequently the case, or United Kingdom for the packets to take else from having been detained by the their departure from, being from its situ government authorities to bring home ation nearer to, and in direct communi. despatches of importance. cation with Manchester, Birmingham, 3. With respect to the Editor of the Sheffield, Glasgow, &c., where about Bristol Magazine's remarks regarding nine-tenths of the letters go from, and the voyages of the Britannia and the also from the great number of American Great Western in October last, the vessels that enter the Mersey, the chief causes of the delay of the former vessel seat of our American trade. Having de are so well known, that it would be quite cided on Liverpool, the contract for con superfluous for me to make any remarks veying the mails was offered publicly, respecting it. and the British and North American 4. With regard to the delivery of letSteam Packet Company offering the most ters via Bristol:-if both the steamers favourable terms, the contract was given were off Cape Clear at the same time, we to them, and not to a company with a will allow that it would take the Bria single vessel, sailing from a second-rate tannia even ten hours longer to deliver seaport to a foreign one.

her letters in Liverpool, than it would 2. With respect to the “wisdom of the Great Western hers in Bristol ; the government” in thus conferring the letters from Bristol are absolutely thirty contract upon Liverpool :--the govern hours in reaching Liverpool by the rement had not only the “exigencies of gular post, that is, if they are posted in the post-office service" in view, but look the former town on the 21st, in time for ing rather farther than the Editor of the the evening despatch, they are not deli. Bristol Magazine, they had also an eye vered till the morning of the 23rd in the to the welfare and benefit of the nation at latter town, thus losing twenty hours at large; for, in the contract, it was ex least in the delivery. If the difference pressly stipulated, that the company is so great with respect to Liverpool, it should provide four steamers of certain follows that it must be much greater with dimensions; and, that in case of war oc respect to the other towns I have mencurring with any foreign country, these tioned. vessels were to be manned and armed in I have drawn my letter to such a length, the same manner as the navy steam-fri that I have hardly room left to make any gates, and were to be placed at the abso further remarks. Still, I cannot conlute control and disposal of the govern clude, without noticing the absurdity of ment during the continuance of such war. supposing that government would give Even if the government had only the the contract to a company with a single "exigencies of the post-office service” in vessel to convey mails of such importview, what is the result? As far as re ance; when, if an accident occurred to gards the “speed" of the vessels, we the vessel, the communication between find that the Halifax boats, in fine wea the two countries would have to be susther, have usually made the voyage home pended whilst she was undergoing her from that port to Liverpool, in from ten repairs. days and ten hours, to eleven days; while Hoping, that in justice to this port, the Great Western takes from thirteen to you will insert the foregoing remarks in fourteen days, although Halifax is many your able and well-conducted Magazine, degrees farther to the northward than I am, sir, yours very truly, New York, and consequently the former

A CLERK, Liverpool, February 26, 1842,

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