there is a breakwater attached by hinges to the lock to prevent the water from rushing too suddenly on to the boat in the lower lock.

MACHINE For cutting DOVETAILS AND TENONS. Thomas J. Wells.-The construction of this machine exhibits much mechanical skill. The cutters are attached to the periphery of a wheel on the end of a mandrel, and the wood to be tenoned is put on to a second mandrel, parallel to the first, the two being made to turn in the same direction, and with equal velocities. If the tenon is to be of four sides, four cutters are so arranged as to divide the periphery of the cutter wheel into four equal parts; and if the tenon is to be cut on two sides only, then two cutters are employed, and placed opposite to each other. As the cutters revolve they gradually approach the axis of the second mandrel, on which the wood is placed, until they reach a line passing through the axis of the two mandrels, and then they gradually recede from it.

The claim is to the before-described "mode of cutting tenons, or dovetails, or other forms, by a similar, simultaneous, rotary motion of the circular plane, and substance on which the tenon, dovetail, or other form, is to be made: the cutting being performed on an increment tangential line to the circumference of the revolving circular plane, whilst the cut made forms the chord line of a segment, on the piece of the circu lar rail cut away by the revolving cutter."

AN IMPROVED BRIDGE. -Earl Trum. bull. This bridge, as described, is to be constructed of iron. It consists of arched truss frames, made in sections, the end of each section having a half post, and this, when united and tied to the half post of the next section, forms an entire post. These sections are farther sustained and connected together by suspension rods, which run from the upper part of one end section to the other, passing under the bottom of the middle section; and by tie rods that run from end to end along the lower line of the truss. The truss frames are connected together by transverse cast iron beams, or sills, on which the floor is laid, formed of a bottom and top plate connected together by diagonal braces, all cast together. In addition to these, the trusses are farther connected by diagonal tie rods, running from section to section, under the floor.

IMPROVEMENTS IN THE ARGAND BURNER, FOR BURNING CAMPHINE AND OTHER

CHEMICAL OILS. Stephen J. Gold.-The claim is to the "mode of compressing the wick by means of two thin, moveable, metallic, cylindrical tubes, combined with the wick case, the two cylinders or wick tubes with

the wick compressed between them being inserted into the annular space between the two cylinders of the wick case, with a portion of said wick tubes extending above the wick case, to allow of their being kept cool by the draught; and also for combining with the outer cylinder of the burner and the rod supporting the button, a moveable cylinder, or screw, disconnected from the rod, but having a button plate which, when the cylin der is turned up, presses against the rod and elevates it: and allows it, when turned down, to return either by its own weight, or by the action of a spring."

PORTABLE SAW MILL, FOR SAWING TIMBER WITH THE CIRCULAR SAW. George Page. In this mill, the shaft of the circular saw has its bearings longer than the width of the boxes in which they run, so as to allow it to have free end play, and the saw is embraced on each side, just back of the teeth, between two friction rollers, which serve to guide it. Each of the guide rollers is attached to a separate plate, the two plates being placed one above the other, and provided with a slot for securing and setting the rollers. The carriage is made in sections for the convenience of transportation, the different sections being united by means of a rack rail at the bottom.

INDELIBLE INK. Thomas J. SpearThe following is the whole of the specifica tion, viz:-"Take three drachms of the least bruised India ink, and four ounces of boiling solution of caustic soda, and mix these together, and shake the mixture well for about ten minutes, when the indelible ink is produced."

MACHINE FOR CUTTING SHEET TIN, OR OTHER SHEET METAL, AND GLASS, Andrew Tracy.-This machine differs very little from other machines for the same pur. pose, which have been patented. The plate of metal to be operated on is held between two plates, each of which is attached to a rotating spindle, the uppermost being provided with a spring, which bears it up when not acted upon by an eccentric lever, by which it is forced down to hold the sheet of metal. The spindle of the upper plate is provided with a lever, with which to turn it when desired; it is furnished with a pall, which catches into the teeth of a ratchet wheel attached to the spindle. In operating with this machine, either the holding plates, with the sheet metal, may be made to turn, or the shears may be carried around the holding-plate, at pleasure.

IMPROVEMENT IN THE COOKING STOVE, CALLED THE FRANKLIN ECONOMY COOKING STOVE." Mathew Stewart.-This stove contains a reflecting oven, the form of which is that of two truncated pyramids, united

at their bases, the inclined surfaces being intended to concentrate the heat in the centre. Each end of the oven is attached to a semicylindrical furnace, the chords of which are towards the centre of the oven. Over the furnaces there are openings for smoke pipes, and for cooking utensils.

FLOUR MILL. Andrew D. Worman.The middlings, which are to be mixed with the fresh ground chop from the burs, are put into a hopper prepared for that purpose, which hopper is so placed that the middlings contained in it shall be conducted from it into the spout or trough, in which the elevators are carrying up the fresh ground wheat to the hopper boy; and to the hopper containing the middlings is appended a shoe and a sliding shutter, in the ordinary way, for the purpose of regulating the feed from them. In this way the middlings will be perfectly and equally distributed and mixed among the fresh ground chop, and will be, in this state, carried through the respective processes to which the flour is subjected, until it is ready to be packed.

HARPOON FOR TAKING WHALES. William Carsleys.-The flukes or barbs of the harpoon are to be so twisted, as that, after being thrown, it shall, on entering the body of the animal, cut its way in an oblique or spiral direction.

IMPROVED MODE OF PROPELLING SHIPS BOATS, AND OTHER VESSELS. Elisha F. Aldrich. In this improved mode of propelling boats, &c., the wheels are constructed with permanent radial paddles, the ends of which abut against the rims of the wheels, so that the principal part of the water against which the paddles act has to pass in between them, through the space between the inner periphery of the rims and the centre, or hub, and is forced out by centrifugal power against the water-back of the wheel, thus impelling the boat forward. The wheels constructed in this manner are placed either in hollow trunks or cases, within the vessel, or in similar cases built outside, and open at the bottom, the wheels projecting below the bottom of the trunks or cases; or they may, it is said, be placed horizontally, and act on the water at the sides of the vessel.

SINGLE LINE RAILWAYS.

Sir,-Your polite invitation to me to make any further observations which might seem to me to be requisite in recommendation of my single railway, induces me to trouble you with the following remarks.

The advantages of a single rail over a double one must mainly consist in the saving of expense, which will always be more than half, inasmuch as all the links of con

nexion in the double rail are avoided, as well as the expense of two-thirds of the land over which it passes. The only question appears to be, how far these are objects worth attaining?

It has been said, that if commerce is benefited by the greater outlay, no matter for the ultimate loss to individual share-holders; but this, to me, is problematical, and hence I conclude that, in a single railway, the time lost in crossing at the central point is of no consideration, where the object is such immense saving. And now, Sir, as I think I can make out that in the single railway, of which I have made a correct model, I can considerably lessen the expense of the rail, render it more durable, and put it in its place by the aid of any common labourer, I will endeavour, unassisted by either plan or model, to give your readers some idea of the improvement.

My new rail consists of only two pieces, viz: the transvervse cast iron sleeper, and the railway beam, of which the following is a description. The base of each transverse piece is composed of two square slabs, measuring 4 feet each way, and 1 inch thick, connected together by a third slab of 2 feet in length, 14 foot in breadth, and 1 inch in thickness. On each of the first slabs, in their exact central line, are erected two triangular brackets, whose base is 1 foot long, and perpendicular side, eleven inches; these brackets are cast with the slab, so that the two slabs, the piece that unites them, and the four brackets, are cast in one mass. These two brackets are so separated as exactly to receive and confine the rail, which when laid down occupies only half their breadth, the other half of which is left for the reception of each succeeding rail. The longitudinal sleepers are of wood 1 foot square, and 10 feet long, and each of the ends as far as it projects upon the square slab, is morticed away 1 inch of the lower surface. The iron rail reposed upon them, in its section resembles the letter T inverted (L), with its upper edge rounded off; and this iron rail is secured on the longitudinal sleepers by imbedded screws. Your readers will see by this arrangement, that the transverse pieces and sleepers, will all repose on the same level, and that the morticed parts and brackets will lock them together, and thus secure the regularity of the line.

The peculiar form of the iron rail will, I apprehend, weigh less by the foot than the most elevated of Mr. Brunel's rails on our Great Western, and offers to the wheels of the carriages a rounded saddleback, which is incapable of retaining loose bodies that may fall upon it, and is intended to carry wheels whose circumferences are grooved into the

form of the Saxon arch, wide enough to allow of some lateral action or oscillation, so that the whole pressure will be on the centre of the arch, whose base is never intended to touch the platform of the rail. By this means side friction would be avoided, for the tendency would always be to resume the centre of the wheel, and such a form would render it nearly impossible for the carriages to get off the rail. According to this plan we should also save the expense of transverse pieces of timber kyanized and pitched, together with the cutting, fitting, screwing, and bolting, and the frequent necessity of from time to time screwing up the bolts. I should recommend a space of from 5 to 7 feet between the rails. Its fur

ther advantages are, its simplicity, its intrinsic value, its portability, and its great safety.

By the assistance of a friend who is a good calculator, and concerned in an iron foundry, I find the price of the castings, at the present price of iron, would amount to the following sums.

The transverse piece in one casting will weigh 15 cwt. 2 qrs. 2 lbs., at 41. per ton, 31.; one at every 10 feet is 528 in a mile, which, at 31. each, is about 1,6007. per mile. Rails at 50 lbs. weight per yard, and at 67. per ton of rolled iron, comes, per mile, to 4707.; and thus the expense of the ironwork, per mile, is 2,0707.

I must not forget to add, that the wheels of the working steam-engine should be so constructed, as to have a bite base line of the rail, in contradistinction to the carriagetrains, whose weight would only press on the rounded part of the rail, at their centre, and whose flanges are never to touch the base.

I remain, Sir,

Your obliged humble servant,
G. CUMBERLAND, Sen.

November 9, 1842.

NOTES AND NOTICES.

Steam-baked Bread.-It has been known for some time at Vienna, that if the hearth of an oven be cleansed with a moistened wisp of straw, bread baked therein immediately afterwards presents a much better appearance, the crust having a beautiful yellow tint. It was thence inferred that this peculiarity must be attributed to the vapour, which being condensed on the roof of the oven fell back on the bread. At Paris, in order to secure with certainty so desirable an appearance, the following arrangement is practised:-The hearth of the oven is laid so as to form an inclined plane, with a rise of about eleven inches in three feet, and the arched roof is built lower at the end nearest the door, as

compared with the furthest extremity. When the oven is charged, the entrance is closed with a wet bundle of straw. By this arrangement the steam is driven down on the bread, and a golden-yellow crust is given to the bread as if it had been previously covered with the yolk of an egg.-Annals of Chemistry.

The Perlevesian Spectacles.-Such is the name given to a new description of spectacles, manufactured by Ward, of the Quadrant, and remarkable for their extreme elegance and lightness (whence the name.) A pair of good sized glasses weighs only about a quarter of an ounce. The pebbles have grooves made in them all round their peripheries, for the reception of the frames, and it is by this means the ingenious maker has been enabled to reduce the weight so considerably.

The late Shipwrecks.-Many of the lamentable shipwrecks, which have of late been so frequent on our shores, might to a certainty have been averted, if the vessels had been provided with the marine thermometer, for which the admiralty have lately awarded the inventor, Mr. Clement, a grant of 2001. The Reliance, for example, is stated to have gone on shore in the night, but "when the wind was fair," and it is inferred that "they could never have seen the land;' that is to say, that they had lost their reckoning and did not know where they were. Now if there had been a marine thermometer on board, this admirable instrument would have indicated amidst the thickest darkness their approach to the rocks, in ample time to have enabled them to steer clear of them; and thus, at an expense of some 407. or 501. the lives of 113 persons, and property estimated to be worth 250,000l. might have been saved. So also with the brig Hamilton, wrecked on the Gunfleet sand: the weather was "exceedingly foggy; about four o'clock the word was breakers ahead,' and almost instantly she struck on the sands." With the marine thermometer no such disaster could have occurred; the navigator can steer his way with it as safely, (so far as rocks and sands are concerned,) as in the clearest sunshine. We hope that ere long not a vessel will be allowed to go to sea without one of these unerring guides on board.

To separate Silver or Gold from Lead.-Take a few grains of bone ash, make it into a paste with a little saliva, spread it about one line thick on a piece of charcoal, and make a shallow impression in it, to receive the globule of metal. Expose it to the heat of the blowpipe, so as to burn it white and hard, and then melt the globule of the alloy on it, and keep it in a constant red heat, till the lead is all oxidised. The advantages of the bone ash over the mica sometimes employed are manifold. 1. It is easier to be obtained, and everywhere the operator can prepare a little if he should not be supplied with it. 2. The metal will remain in the concavity of the bone ash paste, and not be liable to run down and be lost, as on the mica. 3. It is never necessary to change the material; the bone ash absorbs the litharge which collects on the mica, and impedes the process, so that the remaining metallic globule has to be transferred to a fresh slip of mica. 4. The colour of the paste, after the operation is finished, gives an indication as to the nature of some impurities of the metal; lead alone makes it appear yellow; a small proportion of copper changes this yellow colour to greenish.-Dr. G. Engelmann.

Intending PATENTEES may be supplied gratis with Instructions, by application (postpaid) to Messrs. J. C. Robertson and Co., 166, Fleet-street, by whom is kept the only COMPLETE REGISTRY OF PATENTS EXTANT from 1617 to the present time).