and he will want nothing but a boiler and furnace!

It would be useless to enter further into the demerits of the scheme. From the Mansion-house police reports a few weeks ago (by which it appears that Mr. Pinkus was bound over to answer at the Sessions a charge of assault upon the Secretary, for not allowing him to inspect the Committee Minute-book,) we perceive that the Directors of the Pneumatic Railway Company are just opening their eyes to its futility, and have been passing some vote of censure upon Mr. Pinkus-why, it is not difficult to divine.

In fine, until Mr. Pinkus can give to air properties which it has not, or rather, take from it one property which it hasits elasticity-no train of carriages will ever yield to the pull of his "atmospheric rope."

THE CASE OF DEFECTIVE VISION.*

Sir,-A letter appeared in the Mechanics' Magazine of the 3rd of December last, from a Manchester artist, under the signature of" W.," stating, that he was unable to distinguish colours, and requesting of you or of your readers information respecting any remedy for the defect.

It is much to be regretted that persons having such a defect as your correspondent, should choose a profession which requires skill in the distinction and distribution of colours, for such a defect cannot be remedied. It is, therefore, only in my power to point out its cause. I presume, by the silence of "W." on the subject, that he experiences no difficulty in seeing objects clearly, and that his only defect is the one he has stated. If this be the case, his defect is not a visual but a cerebral one; for it has frequently been observed that persons unable to distinguish colours have possessed perfect vision. The cause of this apparent anomaly was unknown, till Gall discovered that each faculty of the mind has its seat in a certain portion of the brain, and that according to the size of such portion, so is the power of its faculty, and, that the function of a part of the brain situated at the middle of the eyebrows is the perception of colours.

• See Mechanics' Magazine, p. 164.

The truth of this discovery is every day verified by its being observed that persons who are unable to distinguish colours, have that portion of the brain depressed; a depression which a practical phrenologist would undoubtedly ascertain upon examining the eyebrows of "W.," and which would sufficiently account for the defect, without any reference to the visual organs. In conclusion, therefore, I would advise "W." to restrict himself, if possible, to a branch of his profession in which the perception of various colours is not required, for his defect is one which no culture can overcome.

I am, Sir, Yours respectfully,

GEO. JOHNSTON.

16, Regent-square, Dec. 23, 1836.

THE INSURANCE-COMPANIES AND THE PUBLIC.

Sir,-Be pleased to allow me the pri vilege of a brief reply to Mr. Baddeley's last.

Mr. Baddeley does not answer the objections as stated in my letter, further than by informing us

1st. That Companies are composed of individuals! This startling truth, which certainly does not require the additional sanction of Mr. Baddeley's name-neither proves that he is right in asserting the utter irresponsibility of the Insu rance-Companies-nor that I am wrong in denying it.

2dly. We have the gratuitous assertion that no parallel exists hetween one public Company and another.

Now, the whole nucleus of the question rests on these facts. Mr. Baddeley avoids both. Is it that he dares not to meet the consequences of his argument? or is he satisfied to leave the matter to your readers?

Whether or no the Companies are able to realise the amount of their liabilities to the community, if so called upon to do, is, thanks to the precautions of the public, not likely to be put to the test. It is not irrelevant, however, to remark, that many Fire-insurance Companies were ruined by the late calamity in New York.

Mr. Baddeley says triumphantly, now it is the insurers who complain. They

do complain, and have a right to complain, if sufficient protection be not extended to every description of property, insured or uninsured. Caunot Mr. Baddeley imagine the one description may endanger the other, and vice versa ?

Mr. Baddeley takes exception to the word " Fire-police:"-let any more appropriate be substituted he pleases; at the same time, he should prove that my argument is fallacious, and that the Fire Companies are not responsible, as he tacitly admits other companies are, and as I maintain them to be, one and all.

Till these matters are settled, I appre hend we shall arrive at no very clear conception of the relations existing between the public and the Fire-offices; meanwhile, I recommend "Aquarius" to Mr. Baddeley's notice. I shall not further disturb him in the concoction of his annual fire-report-with which, I presume, he is now engaged-and which will, no doubt, throw more light upon the subject in question,

Bell-Ringing.-Sir, Our indefatigable friend Col. Maceroni has broached the subject of bell-ringing in his last communication, and from the tenor of his remarks upon that subject. it is evident he is not aware of what has already been done towards reforming the present barbarous mode of obtaining the full sound from large bells. I beg to refer him to the 12th volume of your Magazine, page 281, where he will find a chapter on bells, in which the method of pulling the clapper to the bell," occa sionally resorted to, is noticed, and the reason why it is not generally adopted, explained. In the same paper, Mr. Drury's very superior mode of bellringing, or rather bell-tiiking, is fully described; a method so well adapted to the object required, that it is a matter of surprise it has not been universally employed.--I remain, Sir, W. BADDELEY, London, January 18, 1837.

Triumph of Railways-A Locomotive forcing its way through a Snow Drift.-It was matter of some curiosity whether or not the engine could continue to work upon the Newcastle and Carlisle Railway during the continuance of the snow upon the road. The possibility of so working was fairly put to the test on the 26th ultimo, and the utility of railways demonstrated in a most striking manner, In the deep cutting through the Cowran Hills the snow had drifted to the depth of four or five fe t; and when the Hercules" came down on Monday morning great numbers of country people had assembled to see how he could act in such an emergency, and to render any assistance which might be necessary. On arriving at the spot the engine made no bones of the matter, but dashed right into the drift, clearing his way through, apparently

without the slightest difficulty, the snow at the time flying over the top of the engine chimney like foam from the broken waves of a violent sea; and notwithstanding this and other similar obstructions, the train came down from Greenhead (twenty miles) in an hour and a quarter. The trains have continued regularly to keep their time, while all communication by common roads has been more or less most seriously obstructed, if not entirely cut off for a time.-Carlisle Paper.

The Gresham Lectures are now in course of delivery at the old locality,-up stairs at the Royal HiExchange, near Effingham Wilson's corner. therto, they have been attended by sufficient numbers to compel the lecturer to go through his task, which he declines to do when less than the canonical number, three, are present. Worse than this, reporters have the audacity to take down the lectutes in shorthand, and a contemporary periodical threatens to publish the whole seriatim-if the patience of the public should hold out.

Steam Communication with India.-At a meeting, last week, of merchants trading to India and China, held at the Jerusalem Coffee-house, a resolution was unanimously passed in approval of the project for effecting the communication by steam via the Red Sea. It is a pity the meeting did not go further, and forthwith resolve to petition Parliament. Half-a-dozen petitions, from London and the principal outports, would do more, in conjunction with those already in the hands of Lord W. Bentinck and Mr. Crawford, from Madras and Calcutta, for presentation early in the ensuing session, -than fifty meetings where "resolutions", are passed, and there an end.".

Errata. Page 262. 1st column, 10th line from the top, instead of "nearly four millions," read "nearly four hundred millions."

Same page, 2nd column, 29th line from top, for "Have cut one gash," read Have only to cut a gash."

Page 263, 1st column, 16th line from top, for "useless" read "useful.”

WEST'S PATENT FORGE-BACKS. The rapidity with which forge-backs of the ordinary construction are destroyed by the intensity of the heat to which they are continually subjected, has led to the invention now described, and which was patented by Mr. West, of Crayford, a blacksmith, in December, 1834. The invention consists in the introduction of a current of water behind the forge-back, which, as is obvious, preserves the metal from destruction by the fire.

Fig. 1 represents a front view of a forge-back, which is made hollow in order to admit of a flow of water.

Fig. 2 is a back view of fig. 1, by which the position of the circulating pipes is shown.

Fig. 3 is a side view of a forge-back.

Fig. 4 is a side section, by which the action of the water will become more evident, the arrows indicating the flow of the water.

The back of the forge is made up of two parts, a and b-the part a being the front or part against which the fire or hot coals lie, and is consequently that part in the ordinary back which is liable to be quickly destroyed; but when constructed in such a manner as to admit of a constant flow of water against the back surface, this part a will be less prejudicially acted on by the hot coal, owing to the heat being constantly conveyed away by the circulation of the water. b is the back part of the forge-back. These parts are kept together by screws. d is the induction-pipe, and e the eduction-pipe, which respectively lead from and to a tub or vessel containing water, which is placed in any convenient situation in order that water may constantly flow to and from the hollow forge-back ab.

The advantages of these backs are their indestructibility-that the clinker does not adhere to the back, and consequently that the fire need never be disturbed for the removal of the clinkers-that they always burn cool; and as every smith is aware that they never work so comfortably, nor get their heats so well as they do while the back of the forge continues cool, this must be a great recommendation.

There is also a positive saving of more than 20 per cent. in coals.

The tub or vessel for the water may be placed in any part of the shop, so that it is above the level of the back, and one

tub or vessel will do for any number of backs.

The back is to be connected to the reservoir or tub by leaden pipes.

PHENOMENA PRODUCED BY

ME

ON THE WATER UPON HIGHLY-HEATED TALS. BY CHARLES TOMLINSON, ESQ. Sir, I have read with considerable interest the "Report of Experiments ou the Explosions of Steam-boilers,” copied by you from the Journal of the Franklin Institute, and particularly that part of it referring to Klaproth's experiments relating to the conversion of water into steam by highly-heated metals; but I was disappointed on finding that results only were stated, and no attempt made to elucidate the cause, or to obviate the consequences of the remarkable phenomena referred to.

The subject has engaged a portion of my attention during the last three or four years; some time ago I wrote, but did not publish, a paper on this subject, and have more recently enlarged the inquiry. You will probably allow the matter to be of sufficient interest to insert what I now send you, although I fear it will be found tedious to your readers, since my results are not altogether new-for, indeed, long after they were obtained I met with, from time to time, papers on the same subject when I little expected to find them, containing experiments similar to my own, although affording in some cases dissimilar results.

This has hitherto discouraged me from publishing; and I should not attempt to do so now. but that the American Report has imparted a freshness to the subjectand I do hope that this paper will excite inquiry among the numerous and highly intelligent, as well as practical, gentlemen who contribute so largely to your pages.

When water falls upon a red-hot iron plane surface, it suddenly divides into drops-each drop assumes a spherical form, rotates, and remains upon the plate longer than would seem natural, considering the high temperature to which it is exposed. Now, if a platinum crucible be brought near to a white heat, and water be allowed to fall into it drop by drop, the crucible may be nearly half filled with water, and be kept in this

state for some minutes without any perceptible evaporation. A piece of cold glass or metal will receive no deposit of moisture if held for a moment within the crucible (although the temperature of the water is supposed to be nearly double that of boiling water), and the water suffers diminution almost imperceptibly. In this state the water will be observed to be in rapid motion, rotating "about an axis perpendicular, or nearly so, to the lowest point of the dish, and at the same time its figure changes, and, from being circular in its horizontal section, becomes of an irregular oval, which contracts and dilates alternately as the mass revolves; the transverse axis contracting until its place is occupied by the conjugate, and vice versa. The direction of this rotation is not at all uniform, and the mass sometimes becomes quiescent, and then assumes motion in an opposite direction. When this state of things first begins, vapour sometimes bubbles or bursts up through the liquid; but when fully established, it is most copiously given off be low. In fact, the appearance is that of a stratum of vapour between the water and the bowl, which becomes at times visible when condensed at the edges."American Report, see Mech. Mag. vol. xxv. p. 166.

The foregoing extract, which applies to water in a heated copper bowl, expresses with tolerable accuracy the phenomena resulting from water in a heated platinum crucible. Much, however, depends upon the quantity of water employed, and the surface upon which it falls. If the platinum crucible be large, and the bottom slightly convex within, the water on reaching the bottom divides into globules, each of which is a perfect sphere, and rotates with great rapidity upon its vertical axis, and at the same time it has a dancing, onward sort of motion. If the bottom of the crucible be quite flat, and be kept exactly horizontal, similar effects encue; but the experiment succeeds best when the interior of the crucible is a portion of a hollow sphere, and the inner surface perfectly elean and bright. The water must fall in slow drops, or the surface of the metal will be wetted and steam generated, immediately such is the case; but if the former plan be adopted, there is, accord. ing to my view of the case, an atmosphere of steam immediately formed

which surrounds the globule, prevents its contact with the heated metal, and so protects it from vaporisation.

These facts are remarkable enough, and it is no less remarkable that if the source of heat be removed, and the crucible allowed to cool for a few minutes, a portion of the water will suddenly burst into vapour and be dissipated immediately.

It will be seen, then, that as an excessively high temperature is unfavourable to the production of steam, so, by a converse analogy, water, if kept perfectly tranquil, may have its temperature lowered below zero without freezing. Neither of these facts has, I believe, received an adequate explanation. My present purpose is to confine myself to the former.

Rumford explained the phenomenon by supposing it" due to the reflection of caloric operating on the surface of the drops of water." Pouillet attributes it to another cause. He believes that "the calorific rays emanating from the vessel traverse the water too easily when they are very hot." These opinions are cited by Dumas (Chimie Appliquée aux Arts, vol. i. p. 32), who seems to feel their inadequacy, and there leaves the matter with the following advice:

"However it may be, the fact is incontestable. It ought to caution us against the accidents which a steam-boiler is liable to produce when raised accidentally to a very high temperature, for it might happen that it ceases to furnish steam, and, nevertheless, a reduction of temperature would cause an explosion. Plates of fusible metal are above all things useful in preventing accidents of this kind, since they limit the temperature that can be obtained by the apparatus; for it is evident that a valve would-not be raised at the moment when this singular phenomenon should display itself.

"This kind of accident must be uncommon with ordinary boilers, but it may become very frequent if the employment of generating tubes becomes more common. These tubes containing but small quantities of water, and being habitually raised to a very temperature, it would be easy to attain the very point at which this very phenomenon would ensue. But, in truth, accidents would be less serious on account of the small size of the apparatus."

If I understand this caution rightly, it appears that an explosion may happen somehow in the following manner- -A generating-tube is intensely heated, and