spheric air, which condensed air is to be afterwards applied as a motive power, to machinery. The mode of condensing conssists in placing a reservoir in the water, which 2 shall rest on the bottom. This reservoir is to be open at bottom, to admit the water, but closed at top, to retain the air; the top is to rise to a convenient height above the line of high water; at this line there must be a horizontal partition, or diaphragm, furnished with valves, opening upwards, to admit the air as the water rises, and to retain sit in the air chamber when it falls. This chamber is to be provided with suitable screw-valves. to admit of using the condensed air at pleasure;" it is to be "applied like

steam."

"In the falling of the water, there will be a vacuum created, or a tendency to that effect in the air-chamber, or room; and the atmosphere being admitted through a valve, opening inward, will rush with a force proportionable to the base of the airroom, or chamber, and thus a power will be gained, in the falling of the tide, or water, which may also be employed to condense more air, or otherwise, by making the pressure of this air to work a wheel, or piston, as it enters the air-chamber." c. We noticed a patent, obtained, about two 2 months since, by one of the above-named gentlemen, for applying the rising and falling of the tide to the propelling of machinery, and showed that the plan then proposed was old, referring to a former patent for the same thing, and our remarks thereon. Although the mode there proposed is not, we thick, likely to come into extensive use, there are situations where the power obtainable might be usefully applied; but if that now brought forward is interded

as an improvement

thereon, we are very certain that the thing will be "mended worse." To use the con-ndensed air to advantage, would be an undertaking of great practical difficulty, and, in the present case, could not be effected, but by a very considerable loss of power; the patentees, however, have furnished us with no plan for doing this, and we will not attack windmills. We do not know even what they mean by screw-valves;" these are certainly novelties in mechanics. There is no point more clearly ruled than that a patent cannot be sustained for a principle, but only for the carrying of a principle into effect by certain means; but, in the case before us, no means are given.*

66

CALENDERING CLOTH, Zenas Bliss Johnston, Rhode Island. The improvement here patented consists in the addition of a roller above the three ordinarily used in calenders, by the aid of which additional roller the cloth

See Mech. Mag., vol. xvi. pp. 375 and 436.

is twice glazed in its passage between the rollers, thereby preventing the necessity of performing the operation a second time. In the ordinary calender, it is said that the boxes in which the gudgeons of the top roller run, last generally but sixty days, the weight having to be applied on them, whilst by the new arrangement, in which a large roller with a slow motion receives the weight, the boxes will last for two years.

MANUFACTURE OF TUBES AND HINGES, William Shaw, Buffalo -The machine intended to be described is one for bending sheet metal to form the tubular knuckles of hinges; the description is a very imperfect one, and there is not any claim made; we think, however, so far as the materials before us will justify an opinion, that the machine is sufficiently original to be claimed as a whole. The sheet metal is to be passed in between two blocks of steel, and held in its place by a tightening screw; when, by turning a crank, the end of it is bent round a pin, which pin is to be pushed out by placing the hand upon a lever, thus forcing up a round punch, or wire, for that purpose.

ARTIFICIAL STONE, &c., Charles Clinton, New York.-Limestone is to be burnt until about two-fifths of it is converted into lime; to four bushels of this, when cool, four pounds of pearl-ash and three pounds of alum are to be added, and the whole ground fine; the composition is to be put into open barrels, and to remain there until the lime is perfectly slacked, after which it is to be mixed with water to a proper consistence, and used as a hard finish for walls; when rubbed down, it is to look like polished marble. For outside walls, about one-third part of sand is to be added. The composition may be variegated in its colours by the addition of proper materials for that purpose, and a variety of modes are suggested for varying the ornamental appearance of it. "Blocks, pillars, &c., may be formed of the cement, and, when sufficiently dry, may be plastered, as before directed, and polished."

MR. HANCOCK'S STEAM-CARRIAGES. Statement of One Month's Performances on the Paddington-road, from May 16 to June 15. 42 trips from the City to Paddington. 116 Islington. Number of passengers carried..2970. On the occasion of the opening of Moorgate-street by the Lord Mayor, on Monday last, the "Enterprise" entered immediately after the train of Aldermen, when one of the City officers mounted the roof, waving a large flag. The steamer was full of passengers, and loudly cheered by the populace.

NOTES AND NOTICES.

lar notions must always be a su and interest to philosophical inquirers, whether these notions are founded on observation, or confounded with superstition; not aware are extensively diffused that any popular notion is more among millers though many of them may not be lieve in it), than that which ascribes a greater velocity in the night than in the day to a waterwheel under the same head. Why there shoul be any difference, none of the believers in this doctrine have even been able satisfactorily to explain. To argue against it has been futile, because early prejudice was stronger than the powers of reason; and, therefore, no other way remained that could prove effectual, but to bring it to the test of experiment. For this labour we are indebted to Professor Cleaveland. His state me t, which follows, is contained in a letter to Professor Silliman, and published in the American Journal of Science and the Arts: In a former letter I mentioned the opinion existing in this part of the country, that saw-mills move faster during the night than the day. The explanation usually given by the workmen is, that the air becomes heavier after sunset. I selected a fine day in August, and requested that all the mill-gates might remain stationary for twelve hours. At two o'clock p. m. I suspended a barometer in the mill; the pressure of the atmosphere was equal to 30 19 inches; the temperature of the water just before it passed the mill-gate was 72° Fahr: The log was then detached from the saw, and the number of revolutions of the wheel, being repeatedly counted by different per sons, was 96 in a minute. At midnight I again visited the same mill. The barometer stood at: 30-26 inches, the pressure of the atmosphere hav ing increased seven hundredths of an inch. The temperature of the wa er was 720, the same as at the preceding observation, although it had been a little higher during the afternoon. The log being de ached as before, the wheel was found to revolve precisely 96 times in a minute, showing the same velocity as at the preceding noon. The depth of the water was the same during both experiments. The workmen were satisfied that the result of the experiment was correct, but still they seemed to believe that it would be different in a cloudy night."-American Railroad Journal.

To Purify Cold Short Iron, a very simple process is practised in some bloomeries, which consists in throwing on the loupe at the moment when it is formed, half a shovel full of powdered flux, and keeping it afterwards exposed to the air of the bellows for a few moments, before it is carried to the hammer. The flux thus employed is a limestone, which yields lie of good quality. Its effects on the loupe are very proinpt, depriving the iron of the siderite or phosphate of iron, which, as is well known, renders the iron brittle when cold. -Ib.

Method of Bronzing Iron and Gun-Barrels.Gun-barrels when damasked are ess liable to rust, and any of them, of whatever price, may be treated by a very simple method, which will diminish their readiness to oxydise. When the iron is well scrap d and cleaned, cover its surface with a coating of butter of a timony. If one is not sufficient, two or three coatings may be given. The iron thus acquires a horny reddish brown colour, which is not unhandsome, and which preserves it from rust. When the iron has acquired the desired tint, wipe it carefully, warm it a little and then rub it with white wax, until there remains no longer any visibie traces of the wax. This renders its preservation complete.-Ib.

A good Safe, or victual-preserver, is prepared making it of a double esse of wire-gauze, and fill

ing the interval with fresh charcoal, In fine pieces: Fresh meat, when suspended by hooks from the top, will keep good and sweet for a week in this

safe, in the hottest weather.-Ib.

Method of Coating Busts and Plaster Casts, so as to give them the appearance of Marble; by M. Pleuvarre.-Into a wooden tub or trough, put a strong and warm solution of alum. Into this plunge the bust or plaster cast, previously ma e perfectly dry, and let it remain therein from fifteen to thirty minutes; then suspend it over the solu tion, that the super pour over it a fresh portion of drain off,

lled fore show how the pump may serve ·„atug as a regulator. The feed-pipe, u, v, must -940 be connected with the boiler at the top wowater line, as E, E. Now, if the pump bas supplies water faster than it is evapora 119 ted, and the top water line, E, E, rises Uso as to cover the opening of the pipe, the pipe would be filled with water in sdstead of steain, and, consequently, the crollwater in the plug, A, B, could not dedescend. When, however, the top water 2 line, E, E, of the boiler, descended be low the opening of the pipe, w, v, the pump would again operate to supply 2 the boiler. In this manner, it would work so that, if properly adjusted in the first instance, the water in the boiler e would always be continued at its proper 9 height. It will be seen that, every time suthe pump, or plug, A, B, discharges its gol contents into the boiler, the chamber of

the plug becomes filled with steam, Sand will be allowed to pass off and out condense, when the opening of the is plug connects with the tank. This process, it must be evident, will be an advantage, rather than otherwise, as much of the caloric of the steam will thus be imparted to the water, previous Sto its passing into the boiler. I have preferred describing the above ap-2 paratus, as it is the most simple in its construction, and, therefore, more easily to be understood.. The same rend, however, may be effected by a very different arrangement, as will be seen 10 by reference to fig. 3. Here, A, B, re

presents a hollow plunger, being turned 91smooth and true où its exterior surface, sand inade to work up and down through two stuffing boxes, E and F, placed on the ends of the hollow cylinder, or box, CD. The plunger has three openings, o, p. q, for it may be one long slit from o to q) for the purpose of allowing the water to flow into and out of the chainber, C, D, through the hollow plunger; the small tube, or channel, r, s, is to allow the steam to enter at the top of the chamber, C, D, in order that the water may flow freely out from the chamber into the feed-pipe, v. If we suppose the water tank, K, L, fig. 1, to be placed on the flanch, t, u, fig. 1, and the plunger, A, B, to be connected with the engine, so as to be caused to move dup and down, as the plunger of the ordi nary forcing pump, it will be perceived that, when the plunger is up, the hole, o,

will be within the tank, and the hole, q, within the chamber, C, D; hence, water from the tank may flow in and fill the chamber, C, D; and when the plunger is down, as is represented in the figure, the hole, q, will be open to the boiler, and the water in the chamber will dedescend, through p and q, into it. The relative diameters of the plunger, and that of the chamber, C, D, may be varied to suit the motion which is given to the plunger.

Philadelphia, February, 1836.

P. S.-I am aware that, in the prac tical operation of the above described pumps, some difficulties will probably occur, but I am fully pursuaded that for instance, when the pump is designed they are not insurmountable. Thus, to regulate the quantity of water to the

boiler, as it would be necessary to have the connexion of the feed-pipe with the boiler near the top water line, the water from the boiler would frequently rise in the tube, and run up to the pump before the body of water in the boiler ha risen to cover the opening of the feed-pipe. This difficulty would be remedied by a small tube from the top of the boiler, fig. 1, to the opening, y, in the casing of the pump.

REASONS AGAINST THE DUKE OF WELLINGTON'S INTERFERENCE WITH THE RAILWAY SYSTEM.

[We extract the following very judicious observations on this head, from a appeared in the Courier of Tuesday, letter to the Duke of Wellington, which June 7th.]

It is the peculiar characteristic of this country that great public works can be executed by private capital and enterprise without assistance from the public purse; and to the encouragement which this spirit has received under a free and constitutional Government, may be attributed the vast benefits which the nation has derived from its canals, its docks, and other public improvements.

Wealthy individuals have been found ready to advance their capital for such works, because they could rely on the good faith of the Government and the country at large in seeuring the possession of their property.

It is, therefore, the duty of Parliament to take care that in their endeavours to protect the people from the consequence of a possible monopoly in these works, they do not run into the contrary extreme, and, by ill-advised