persuaded that if the value of the principle were appreciated as fully as it deserves, all practical difficulties, if such there be, would speedily be surmounted, and that steam would be used of a pressure which is now unheard of, and would be employed expansively to an extent which, under present circumstances, would appear perfectly unattainable.

It was with great pleasure that I heard Mr. Russell, at the recent meeting of the British Association, in his admirable address on the improvement of steam navigation, express opinions in favour of the same principle which I have recommended; viz. the substitution of high pressure steam and its employment expansively.

Newcastle-on-Tyne, 1st Sept. 1838.

W. G. A.

PRICE'S ADJUSTING ROUND-SOLE

PLANE.

Sir, I am a carpenter and patternmaker at the iron-works which are conducted at this place, and in the course of my business have practically found the great inconvenience and expense attending the plan at present in use of planing concave surfaces of different

curves.

You are no doubt aware, that for any change in the radius of the curve, it is necessary, with the circular planes or round-soles at present used, to cut away a certain portion of the plane in order to adapt it to the new curve required, and consequently by successive alterations the plane is destroyed. This evil I have remedied in my own case, and feeling the advantages which I have derived from my invention, I take the opportunity afforded me by your widely-circulated Magazine tò draw the attention of my brother workmen to it. My plane (which may be called the adjusting plane) is fitted with a loose plate of elastic steel, the two ends of which are made to approach or recede from the convex surface of the wood by means of screws passing through holes near them. It will be at once seen that by merely turning the screws the curve of the plate may be varied from any convexity which may be given to the wood in the first instance, to the straight line which the plate would assume if left to its own elastic power. The part through which the groove for the iron passes,

is strengthened by an additional piece of steel, about a quarter of an inch thick, brazed across the inner side; which piece serves also to fix the plate in its due position, being let into the wood. The counter-sunk heads of the adjusting screws work also in small blocks similarly brazed and let in.

This description will, I trust, enable my fellow-workmen who have occasion to use circular planes or round-soles, to avail themselves of an improvement from which I have myself found great advantage. Should you agree with me in this, you will, perhaps, permit the insertion of this letter in your valuable Magazine.

I am, Sir,

Your obedient servant,
REES PRICE.

Vartig, near Pontypool, South Wales,
August, 1838.

EXPERIMENTS AND OBSERVATIONS ON THE COLOURS OF THIN PLATES. BY CHARLES TOMLINSON, ESQ.

Sir, The various modes of obtaining the rings of Newton and the colours of thin plates generally are well known: 1st, by the thin film which the soap bubble affords; 2nd, by the thin film of air obtained by superposing two lenses; 3rd, by laminated substances generally, such as talc, mother-of-pearl, selenite, &c.; 4th, the ingenious method of Nobili by means of galvanic agency, as developed by him in his system of metallochromy; and 5th, by films of oil upon the surface of water. These and other modes are so well known, that any new modes of multiplying them can only be regarded as new variations of old facts, and therefore not sufficiently important to present for publication.

My object in this paper is, to offer to the notice of scientific men some new facts connected with the colours of thin plates.

If a single drop of olive, rape, or castor oil, or of copaivi, Peru, or Canada balsam, be placed upon the surface of clean and perfectly still water, contained in a clean glass goblet, and placed in such a situation as to receive the light of day, a film will be formed upon the surface of the water, the thickness of which varies from about 0.38 to 57.75 millionths of an inch, and in some cases

where white light only is reflected by the film, the thickness thereof is greater. Some of the oils and balsams require to be heated before they are dropped upon the water, because, at the temperature of the air, their viscidity is too great to allow of a diffusion over the surface of the water.

From the above oils and balsams I will select two, viz. oil or spirit of turpentine, and balsam of Peru.

A small portion of spirit of turpentine being taken up on a glass rod, a single drop is allowed to fall upon the surface of the water—this drop immediately expands into a circular form, the diameter of which is about 1 inches-it reflects white light, but no colour whatever for a considerable time, until, by evaporation, the film becomes sufficiently thin. If, however, as soon as the drop of turpentine has fallen upon the water and expanded into a film, we hold over the film, at the distance of about one-sixth of an inch, a glass rod, or the finger well moistened with sulphuric ether, a splendid display of Newton's rings is instantly obtained, which continue until the ether has evaporated. The centre of the orders of rings is immediately below the end of the rod or finger; but their form is subject to variation according as the article dipped in ether varies.

The rings generally close up and disappear as soon as the influence of the ether is removed from the film; but as soon as the ether is removed, the rings lose their perfect form as circles or ellipses, become broken up, and a variety of colours is seen, which depend upon varying thicknesses of the film.

If, now, we dip a clean glass rod into nitric acid, and hold the wetted end over the film, the latter begins to contract in dimensions until a certain thickness is attained at which all colour disappears; and a film of the size of a crown piece is soon reduced to one the size of a sixpence. On again applying ether the film expands rapidly, and the rings are developed as before.

These results are also obtained when the film is formed from animal and vegetable oils and balsams. Lignor ammoniæ, pyroligneous ether, alcohol and naptha, have, the first by its gas, and the rest by their respective vapours, a similar effect upon the films as vapour of ether.

When a drop of balsam of Peru is allowed to fall upon the surface of water we instantly get a magnificent display of coloured rings: on applying vapour of ether, ammonia, &c. to any part of the film, its thickness is instantly reduced, so that the colour belonging to one order of Newton's rings is instantly exchanged for the colour of one of the series above it.

A magnet seems also to have an action upon the film, the north pole tending to repel it, and the south pole to attract it. But the magnetic, as also the galvanic and electrical results, which I have as yet obtained, are not sufficiently satisfactory for me to speak decidedly in this communication.

I have carefully abstained from all theory in this article: the above is a short extract from a large variety of results which I have obtained in an endeavour to substantiate a principle of chemical repulsion in contradistinction to chemical attraction. I wish to give immediate publicity to the above facts, and if you will oblige me by inserting them in your next number, I will send you another article on the same subject in a few days.

Salisbury, August 23, 1838.

ARTIFICIAL FUELS.-WELCH COALS.

MECHANICAL FLYING.

Sir,-You will have, doubtless, perceived by the newspapers that the authorities at Woolwich, have, like many others, taken a leaf out of your book, without any acknowledgement.

In No.

170, Nov. 25, 1826, twelve years ago, may be seen a letter of mine in which Í recommended the use of fat, oil, or coaltar, combined with coal or cinders, (for a wick, as it were) for the use of sea-going steamers. I further suggest, that melted fat, oil, or coal-tar, might be injected into the incandescent coal or coke, through "little beaks in the sides of the furnace, and performed by the engine itself, under the complete control of the engineer." I add, that oil, either animal or vegetable, and wood, are often to be procured where no coal is to be had; and that a wood fire, with the regulated projection of oil upon it, would produce a clear flame and great heat. Coal-tar burns at a far lower temperature than oil or fat, and produces vast quantities of smoke and soot.

Some time in 1833, I think it was, another correspondent of yours, described his process for making an artificial fuel or coal, by working up coal-tar, dry clay in powder, and saw-dust, which were formed into brick-like shapes, just as the Woolwich gentlemen have now invented, for the third time, at least.

I take this opportunity of submitting to the consideration of those concerned in sea-going steamers, that from experiments I have made, I am decidedly of opinion that the real Welch stone-coal will be found to double the work of any other coal or coke; and consequently, that one ton of the former will propel a ship as far as two of the latter. With some furnaces, it may require a first charge of Staffordshire, or other quickburning coal, to ignite it, but once well lit, its durability is quite surprising, and without any smoke whatever.

Should any one of your monied readers be desirous of immortal fame, he will patronize my invention of flying in the air by purely mechanical means, and so confer on mankind dominion over the air, as they already have over the sea, which will effect a greater change in our physical and moral condition than has any other invention of the last 3000 years. Ye closet doctors, remember the scoffers at gas-steam-printing-and the report of the seven British Admirals, who in 1805, solemnly declared steam navigation on the ocean to be "impossible"! Remember also our own illustrious Dr. Lardner, who pledged all his practical science against the possibility of steaming across the Atlantic, just at the moment that the feat was being achieved! Alas! the scorn with which the Doctors and the vulgar herd, both rich and poor, assailed poor Windsor and his "smoke lights! Poor creatures-to apply the word "impossible" to the merely varied application of a simple mechanical action !

I have the honour to be, &c., F. MACERONI. 3 St. James's Square, August 22, 1838

ROCKETS AS APPLIED TO LOCOMOTION. -BADDELEY'S NAVIGABLE BALLOON, &c.

Sir,-A notice in your 785th Number, page 368, informs us that a M. Jobard, of Brussels, has proposed to apply the force arising from the burning of a pyro

technical composition, to the propulsion of certain vessels through the water, with great speed.

It must be quite evident to a majority of your readers, that in proposing to cross from Dover to Calais in eleven minutes! M. Jobard is propounding what is utterly impossible. It would take him nearly that time if blown from a mortar; but as to attaining anything like the velocity stated, while moving through so dense a fluid as water, it is quite absurd.

The immense resistance offered to bodies moving with high velocity through water is tolerably well known; but a body of suitable form, urged by such a force at a more moderate rate, might traverse the air at will. I have no hesitation in here stating, that one of three plans (the other two being mechanical) by which I proposed to give the necessary impetus to my "navigable balloon, was to employ the reacting force given out by the combustion of a suitable rocket.

The power thus generated is exceedingly great, while the material is comparatively light; and the rocket long since suggested itself to me as being by far the most eligible source of power that could possibly be applied to the purposes of aërial navigation.

A form of balloon susceptible of being thus impelled-and as a necessary consequence, of being guided-through the air, has been designed by

Yours respectfully,
WM. BADDELEY.

London, August 27, 1838.

FLOATING BREAKWATER.

Sir, The Lotus forms a natural break. water on a small scale, intended, perhaps, as a shelter for the spawn and young of fish, and the nestling and rearing of equatic birds. I have often thought that a hint might be taken from nature in this point, to form floating breakwaters, in situations where the formation of harbours would be impracticable, or attended with such expense as to preclude the possibility of undertaking their for

mation.

JOHN NORTON.

23, Upper Berkeley-street, West.