ing the nature of the trial to which it will be subjected, I must leave the public to judge, entertaining the opinion, that a decided preference will be given to bearers buried in and consolidated with a bed of concrete; two feet or more wide and deep, and which, for solidity, strength, and durability, will resemble a continuous rock, the whole length of the road.

Then, the species of wood to be employed for bearers. Mr. Vignoles is for fir, which after being kyanized, he supposes will last seven years; but I am for oak, which after undergoing the same process, will last seven times seven years; and during this period no interruption be occasioned to the traffic, by taking up old bearers and putting down new ones. Again, Mr. Vignoles will secure, (that is, ́if wet, dry, and hot weather permit,) the rails to fir bearers by nails; but screws in oak bearers render my plan independent of the influence of the weather.

Now, as to price: Mr. Vignoles' plan costs 11s. per yard; but I have made known that the maximum price of mine will be 10s., though in many, perhaps in most parts of the country, the price will not exceed 8s. per yard, even if it does 7s.; and were Memel fir to be used instead of oak, and nails instead of screws, a further diminution of 1s. per yard might be made. But who that reflects would thus economize? Mr. Vignoles' iron rail costs 5s. 7d. per yard, but mine only 1s.; and where he uses four feet of fir, I use only one of oak. He has no means for the bars to expand and contract, but upon my plan this advantage is enjoyed.

In conclusion, I thank Mr. Vignoles for his publication, which, on account of its theoretical data, I deem of great valué. THOMAS PARKIN.

Patent Rallway Office, 31, Broad-street-buildings, Jan. 16, 1837.

railway was a good hit, and told well; there are so few who understand the relation between a machine and its model.

Mr. Pinkus, convinced in spite of himself (whether by our remarks or not, we aver not), that his plan would not do; and seeing, also, that this began to be the opinion of some who had at first supported him, he bethought himself of another, and what he calls an improved plan, for which he forthwith took out Letters Patent. Upon this new plan a short experimental line has been commenced by the side of the Kensington Canal. The air-mains or tunnels, however, have been lying there some time, and are becoming rather rusty -operations having for some reason or other been suspended. We hardly know whether it be worth while to enter into the details of a plan, the foundation of which we hold to be absurd; but as Mr. Pinkus evinces considerable ingenuity in his improvement, we shall shortly describe it. He altogether dispenses with the travelling diaphragm, and diminishes the size of his air-tunnels to a fourth of what was originally proposed; in fact, the air-tunnel is the only feature common to the old and new plans.

As we before observed, the travelling diaphragm is now altogether dispensed with. The railway is to be divided into sections of five miles length; at each of which lengths there is to be a fixed steamengine, working air-pumps. The diameter of the mile and quarter of air-main next each station is to be of 11 inches, and the middle 2 miles, to be of 9 inches. The pumps at each end act upon the air in the tunnel, continually rarefying it, as it is thrown in by the working of the locomotive-apparatus. The main is to have an opening in the upper surface two inches wide; on to the edges of this opening are to be attached plates, forming what Mr. Pinkus calls a "metallic valve," made of an amalgam of iron and copper, hard rolled to make it elastic, 4th of an inch thick at the lower edge, andth at the upper (the insides of which are to be polished smooth), and four inches high. The annexed cuts will show the thing more clearly. Fig. 1 is a plan of the valve, and fig. 2 a cross section of the air-main, with the valve attached, and the tongue (afterwards described) between the lips of the valve. In both figures a a are the lips of the valve,

Fig. 1.

Fig. 2.

which it will be seen, in their undisturbed state, by their elasticity press upon one another and form an air-tight joint the whole length of the main. Working between the lips of this valve is a hollow metallic tongue (b, fig. 2,) the shape of which is seen in fig. 1; the sides of this tongue, in contact with the lips of the

valve, are polished, and the tendency of the latter to collapse by their spring, pressing upon these polished sides, as they pass along makes the joint air-tight. This hollow tongue forms a communication through throttle valves with a condenser or vacuum-vessel; and this vacuum-vessel communicates through alternating openings (somewhat similar to those used in steam-cylinders, and worked by an eccentric from the crank), with two cylinders, in which work pistons, whose rods turn cranks, which give a rotary motion to the wheels of the locomotive. The mode of action is as follows:-The air in the main is kept rarefied by the exhaustingengines at each end; a communication being made between it and the rarefied air or vacuum vessel, by opening the throttle-valve-and between the vacuumvessel and the cylinder by the sliding passage, a partial vacuum is formed under the piston, which the outward atmosphere forces down, giving half a turn to the crank; the alternating airpassages are then reversed-the other piston is acted upon in the same wayand a revolution of the crank, and consequently carriage-wheel, is completed. The cylinder-full of air, after having forced down the piston passes into the vacuum-vessel, and through the hollow tongue into the main, from which it is pumped into the atmosphere by the stationary-engines and air-pumps at each end of the five-mile section. As the tongue passes forward between the lips of the valve it will open a passage for itself, which will immediately close behind it by the elasticity of the plates. The tongue is prevented from becoming hot by friction by the current of cold air constantly passing through it from the cylinders. This, we believe, is all of Mr. Pinkus's specification, which is wanted to give our readers an idea of his improvement-there are several minor points which it is unnecessary for us to refer to.

Our readers will perceive from the foregoing sketch that Mr. Pinkus's said improvement is worse than his original plan-inasmuch as he has added complication of parts and weight of machinery. We could suggest an improvement, whereby Mr. Pinkns would save air-pumps and steam-engines at each end of his five miles. Let him make his vacuum after Savery's plan,

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 exa mining 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

ex

do complain, and have a right to com plain, if sufficient protection be not tended to every description of property insured or uninsured. Cannot 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 bell in which the method of " pulling the clapper to the bell," occasionally 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-striking, is fully described; a method so well adapted to the object required, that it is a matter of surprise it has not been uni versally 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 feet; 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 chinney like foam from the broken waves of a violent sea; and notwithstanding this and other similar obstructions, the train came down from Grçenhead (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 Exchange, near Effingham Wilson's corner. Hithert, 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 lectures in short-hand, 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 conjunc tion 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."