cond objection is, "The propellers, when making their return stroke, in a short head sea or ripple, must just produce as much effect to drive the vessel astern as the immersed one drives her ahead." A three-foot crank, we have shown, describes a circle whose diameter is six feet. Now, supposing the paddle to dip two feet, it will rise from the surface of the water four feet on its return; it would therefore be necessary, to produce the injurious effect described by your correspondent, that the vessel should heel sufficiently to dip or bury the paddle six feet under water; in which case I appre hend, not only the propeller but the wheel of the Dundee would be equally useless and inefficient. The third objection is, "The great additional breadth necessary, as Mr. M'Curdy's wheel is twelve feet broad, if the cranks have a three feet throw." Now, sir, I beg to

state that Mr. M'Curdy's wheel is no such thing-the throw of the crank has nothing to do with the breadth of the paddles. On reference to the drawing, it will be seen that each paddle, in revolving, partly occupies the same space as the adjoining one; so that four paddles of three feet each in breadth, only require a space of about eight feet six inches to revolve in, instead of twentyfour feet, which has been so liberally allotted to them by your correspondent. I have seen Mr. M'Curdy's propeller in operation, and have no doubt, that, with a paddle containing half the superficies of one in a common wheel, it would be equally effective, as its action is at all times vertical, and there is no loss of power on entering or leaving the water. I remain, Sir, &c.

FAIR PLAY.

h

Sir, I perceive, from a recent Number of the Mech. Mag., that an ingenious Frenchman is about to take out a patent for that long-sought desideratum, the perpetual motion. Now, sir, as it happens that I have myself lately had the good fortune to achieve the discovery, you will, I hope, admit the propriety of allowing me to enter a caveat in your pages against any foreign rival's pretensions to priority-in case it should turn out, when he enrols his specification, that his method is the same as my own. Thus much, Mr. Editor, is due, even out of bare justice towards the claims of native talent!

My invention (the details of which I

will not trouble you with at present) is founded on the principle of the hydrostatic paradox, as that principle is laid down in the first number of the Library of Useful Knowledge, as follows :—

"We have seen how the displacing any portion of a fluid by a solid, whatever be the weight of the solid, produces no difference in the weight of the fluid, provided it stands at the same height as before; and how raising the height of the fluid by plunging a solid into it, increases its weight. If the fluid is raised by pressing or forcing it upwards, in however thin a column, provided the vessel is kept full, and closed in all directions, the pressure of the fluid will be increased, and the weight of the vessel will be increased, although nothing whatever, either solid or fluid, is added

to it, or made to touch it. The cylindrical box e f (see fig.) has a tube g fitted into its top, and there is a wire D fitted to a plate D, the size of the inside of the box, and moving up and down in it, water tight. The plate being at the bottom hi, water is poured into the box, so that it rises to ef, but does not rise in the tube. It is then balanced by a weight in the scale A. If the wire C is drawn up so as to raise the plate, and force some of the water into the tube, the whole box and water will weigh more than it did; and to restore the balance, more weight must be put into the scale A. If the box is three inches diameter, every inch that the water rises in the tube will add above four ounces to the weight of the box and tube, whatever be the bore of the tube; for the pressure of the water in the box, in all directions, will be increased by the weight of a body of water whose height is the height of the water in the tube, and whose base is the extent of the surface of the water passing on the top e f of the box. Now the top being three inches diameter, its surface is about 7 square inches; and a body of water one inch high, and 7 square inches broad, is 7 cubic inches of water, which weigh about four ounces. Thus, raising the wire a foot, will add three pounds to the weight of the water."—Library of Useful Knowledge, Hydrostatics, p. 6.

It is by a very simple application of the principle thus set forth, that I propose to effect the desired object; and all I can see to wonder at is, that mankind should have been so long without discovering the grand arcanum, when so convenient a law of nature stared them in the face all the while. There are, indeed, some" roaring infidels," who venture to assert that there is no such law in existence, except in the pages of the tract published "under the superintendence of the Society for the Diffusion of Useful Knowledge." But can it, for an instant, be believed that so monstrous a blunder as the laying down, with all due pomp and circumstance, of such a non-existent law, could be truly laid to the charge of a learned body, with no less profound a philosopher than my Lord Brougham at the head of it, and whole scores of men of science of first-rate eminence on its committee? The thing is evidently quite out of the question. A friend of mine, indeed, who delights in throwing cold water on all plans of perpetual motion, did startle me a little by observing, that if the pressure of the water in the box were increased equally" in all directions," the

upward pressure would exactly counterpoise the downward, and that, therefore, the "weight of the box and tube " would remain the same as before! There certainly appears to be something in this objection; but, if it were wellfounded there would be an end at once to my grand project. That being the case, I prefer practice to mere theory, and devoutly believe that, as the com. mittee-men of the Society would hardly allow their names to be paraded on the covers of the book as having superintended its composition, without having actually tested by experiment all the propositions it contains (and especially one so novel and remarkable as that in question), it is absolutely and literally true that the specific gravity of water, at a given moment, may be one, while in the next it may be a hundred, or a hundred thousand! I remain, Sir, Your most obedient servant,

April 28, 1835.

66

F. H.

EMIGRATION TO THE NEILGHERRY HILLS -INDIAN HAND-MILL-CULTIVATING SUGAR IN INDIA, &c.

Sir, The 390th page of your twentyfirst volume has just been forwarded to me by the post, and in it I regret to see a communication which has a direct tendency to discourage the emigration of settlers to the Neilgherry Hills. I know not whence "L." could have obtained his information, that "the greatest part of the land on the mountains is already appropriated," as when I was there in November last, there were several thousand acres of the richest land inviting occupation. His next assertion is more worthy of consideration, and I will endeavour to obtain more certain information on the subject; but from the inqui ries which I have already made, and as far as I can recollect, the aborigines alone are taxed as mentioned by "L." I am nearly sure that the low-country natives, who almost exclusively cultivate potatoes, are exempt from taxation; and that the European inhabitants are, (or rather were when I wrote my last communication,) I am perfectly certain.

You will observe that in inviting the attention of agricultural emigrants to these hills, I never for a moment con

templated their competing with the natives in the cultivation of grain; it is to the cultivation and production of European articles of necessity and luxury, that I would draw their attention. Whatever is required by the natives, is produced by them at so cheap a rate, that it would never repay an European for his labour and trouble; but, I again repeat my conviction, that a limited number of small farmers emigrating to these hills, would have no reason to regret the step they had taken, more particularly if they had a son, or other confidential agent, in whose hands they might trust their produce for sale at Cannonnore, Bombay, Madras, as owing to the dishonesty and pilfering propensities of the natives, Neilgherry potatoes, though they can be brought to Bombay at rs. 2 per maund, are not always obtainable for even 6 rs.

I will take a hint from your correspondent, and proceed from where he has left off.

The only mill in use in India for grinding corn is the hand-mill;* which consists of two circular stones, from fifteen to twenty inches in diameter. The centre of the upper or moveable stone is cut out, forming a hole four or five inches in diameter for the admission of the grain; across this hole a narrow piece of wood is fastened, in the centre of which is a small aperture to admit of the point of a wooden pivot, fixed in the centre of the lower stone; a small wooden handle is fixed near the outer rim of the upper stone. This mill is, according to its size, put in motion by either one or two women, which will probably recall to the recollection of your readers, Matthew xxiv. 41; and in almost every house at the hour of three or four in the morning, a traveller, as he passes through a native town, hears these poor victims of ignorance and barbarous customs commenc

The only windmill I have ever seen in this country, is one at the town of Baypoore, near Calicut, on the Malabar coast, which was erected by the Bombay Government, twenty-five or thirty years ago, at an expense (it is said) of about four lacs of rupees, (40,000l. sterling,) for the purpose of sawing timber; it was found to go at a splendid rate for some time, and the harder the wind blew, the faster it revolved; but like the Dutchman with his self-moving leg, it was discovered, when too late, that a trifling error had been made in its construction, viz. how to stop it, or lessen its speed. It soon afterwards received some injury, and has ever since remained in statu quo, a monument of the folly of the Bombay Government.

ing the labours of the day, and accompanying them with their montonous and unmusical songs.*

In making bread, the dough is kneaded with tarec, which is used in the place of both water and yeast; and when made with care and good materials, the bread is not distinguishable from what is eaten in England.

An immense quantity of sugar-cane is cultivated in India, but by far the greater part is made into "gourr " for native consumption. In Bengal and in the vicinity of Hydrabad, excellent sugar-candy is prepared, though not quite equal to that imported from China: at Hundidroog, near Bangalore, the finest clayed sugar is manufactured; and I once saw a specimen of tolerable loaf sugar and sugarcandy, manufactured on the estate of a Parsee, in the island of Salsette, near Bombay; but these are exceptions to the custom of the country, which is as follows:

In the middle of the cane-field is a pit, about twelve feet square and five deep, along the centre of which, three axles are fixed in a strong frame-work on three perpendicular rollers; the centre fifteen inches, the others one foot in diameter, and about five feet high, made of the wood of the tamarind-tree, on ac.. count of its great strength and hardness; two-thirds of the upper part of the rollers are formed with teeth which fit in to each other; the lower parts are smooth, and meet close together; the upper axle of the centre roller projects above the framework in which it is fixed: to the projec tion a lever is attached, which is drawn by two or four bullocks, and all the cylinders revolve with a creaking noise, which on a still night may be heard at two or three miles' distance. The canes having been cut into lengths of two or three feet, are passed between the first and second rollers, by a man stationed for that purpose, which having been returned to him through the second and third rollers are thrown aside; the juice is conducted through a hollow bamboo into an earthen vessel sunk in the ground at

* Grinding corn, as well as bringing water in earthen vessels from the nearest well, (vide Generis xxiv. 13,) sweeping the house, plastering the walls and floor with "gobur," and cooking the food, are in India the exclusive duties of the female members of the family, while the remainder of their time is employed in spinning and weaving.

the bottom of the pit, whence it is carried in earthen pots to the boiler.

The boiler is a circular copper vessel, the sides of which make an angle of about 670 with the bottom; it is from four to five feet in diameter, and from six to fifteen inches deep, which having been placed over an oblong hole in the ground fashioned for the purpose, the fire is fed with the pressed cane, and the juice boiled, until it assumes the appearance and taste of hard-bake or tom-trot, most probably well known to your juvenile readers; in this state it is sold in the bazaars as "gourr."

Yours, &c.

Guzerat, 1st Dec. 1834.

BERGEIN.

So

To construct a chimney which would carry smoke, has been found in practice one of the most precarious objects of mechanism. little has the theory of smoke and draught been understood, that if ever a chimney was constructed to draw well, it was evidently a matter of accident; for no mechanic seemed to have any rule for constructing chimneys, which would ensure a good one. We have been extremely gratified within a few days, by the inspection of a flue, and a set of fireplaces, constructed upon a plan entirely new in principle, invented by Mr. Henry Antis. We had not the pleasure of seeing Mr. Antis's model; but we saw the practical effect

In the Southern Mahratta country, during the rains, these vess 1s are used as ferry-boats on the numerous rivers which intersect the country; in August, 1832, I actually saw eight men safely ferried across the deep and rapid, though narrow river Malpurbar, in a saucepan of the above de scription.

of his discovery, by a chimney and fire places in operation, in the house of Mr. Joseph Wallace, in Front-street; the success of which is complete, and triumphantly sustains Mr. Antis's theory on the subject. His theory is, that cold atmospheric air tends to the centre of gravity till it meets with some obstruction, which gives it another direction; that heated or magnified air is exactly vertical in motion; that hence the flue to carry it off should be perfectly vertical, and in no place of smaller dimensions than at the bottom or first inlet. He maintains that it matters not how many inlets there be to it, provided the area of a cross section of the flue be equal to those of all the inlets combined; it may be greater, but must never be smaller. He, therefore, starts with a single flue from the cellar, regulating the size, to cover the area of all the contemplated inlets from bottom to top. He carries it up, all the way of the same size, in exact perpendicular direction; nor need the wall be more than the width of one brick in thickness. Wherever he wants a fire-place, he attaches jambs of the usual shape, leaving the common perpendicular wall of the flue for a back; throwing an arch across, at the proper place, in the usual form, covering it tight to the back wall. Immediately opposite, or below the covering of the arch, he leaves a horizontal aperture in the flue, the whole width of the fire-place, from jamb to jamb, in size according to calculation previously made, and according to the height of the arch; which for jambs from twenty-four to thirty inches high, must not be less than three inches perpendicular in the opening.

There seems to be philosophy in this theory; and practice, so far as tried, proves that there is truth in it; and we have no doubt the plan will, on a little further trial, be uni. versally adopted by builders.

Beneath each grate, fitted in a fire-place, is an opening left, which descends obliquely into the flue. In this opening, on a level with the hearth, is a fire-grate fixed, through which the ashes descend from the grate above. And such is the effect, that while a strong current of air is produced, by the heat from the fire in the grate, through the horizontal aperture above, a moderate draught is also maintained in the oblique one below, which carries off all the dust; so that from a coal fire, not a particle of dust escapes into the room. He also affixes a valve to each inlet, hung in such an ingenious manner, that the mere pulling of a small brass knob closes it entirely; and thus, in case the chimney should take fire, all the currents of air may be stopped in a moment, and the fire dies at Not a particle of soot can ever enter your room or your fire-place; for that, as well as the ashes, all descend to the bottom

once.

of the flue in the cellar, where an opening, with a sheet-iron door, is constructed, from which these articles can be taken; and through which a sweep may enter and perform his duties, without disturbing the business, or amusements, or quiet of any part of the family. Where necessary, he also carries up side flues in the jambs, by which air can be introduced, to regulate the temperature of your room, or the force of your draughts.

The advantages of this improvement are, 1st. Fewer materials are used, which cheapens the work.

2d. Less room is engrossed by dead brickwork.

3d. No annoyances from soot or ashes in your rooms-not even when a sweep ascends to clean out your flue.

4th. Power to regulate the temperature of your rooms, without opening doors or windows.

5th. Perfect security against smoke, in every room in your house.

out which there can be no fine needlework.

Needle-threaders, of an expensive and somewhat inconvenient form, have been in use for some time; but in the little instrument now before me, from the celebrated manufactory of Messrs. Joseph Rodgers and Sons, of Sheffield, a very superior and convenient machine has been produced at a cheap rate. Fig. 1 is a front, and 2 a back, view of this threader; it consists of an ivory stem or handle, with a hole at the top a to receive the needle; b is a spring steel plate which holds the needle firmly in its place during the operation; c is a hole in the steel plate where the thread comes through.

To thread the needle, put it with the eye downwards (and in the direction of the thread-holes) into the hole a at the top of the threader, pressing it down as far as it will go. Having prepared the thread in the usual manner, put it through the wider hole d, being careful not to hold it in a slanting direction, either upwards or downwards; from the tapering form of the entrance to the hole d, the introduction of the thread is accomplished with great facility and certainty. This hole being left white, while the other parts of the ivory are coloured, renders it easily distinguishable in a very indifferent light.

These threaders are made of two sizes, marked 4 to 8, and 9 to 12, respectively, which will suit needles of those numbers. Some are made double to suit all needles, having the fine threader at one end and the coarser one at the other.

I have used this instrument myself (experimentally only), and have received such unequivocal testimonials of its usefulness, from several of my female friends, that I think they cannot be too extensively made known, for the benefit of all who need their friendly aid.

They are a pretty addition to the worktable, and fully answer their intended purpose.

I remain, Sir,
Yours respectfully,
WM. BADDEley.

London, May 20, 1835.

REMARKABLE ACTION OF PLATINA ON

OXYGEN AND HYDROGEN.

Sir, My attention has just now been called to a curious fact, disclosed by Dr.