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Invariable Pendulum. - M. Mitscherlich has found by experiments that heat expands a rhomb of calcareous spar in the direction of its axis, and contracts it in directions at right angles to that axis. Sir David Brewster deduces from this fact the following interesting conclusion" As there must be in any given length of massive carbonate of lime as many expanding as there are contracting axes, then if the contractions and expansions in each individual crystal are equal, they will destroy one another; but if they are proportionate to their lengths the contractions will exceed the dilatations. In this case we have only to combine the marble with an ordinary expanding substance to have an invariable pendulum. The balances of chronometers might be thus made of mineral bodies."

The Turning-Lathe.-Sir, In No. 460, Mr. Walker, of Hackney, gives a plan for inspecting the work in the turner's lathe without stopping it and asks whether any of your correspondents have seen similar arrangements? I beg to inform him, the plan he proposes has been for many years in use; and I have seen it at work in the screw-engines both at Tavistock and Birmingham. At Portsmouth and Woolwich arsenals they have a similar plan, shifting (by means of a lever) the band from the pulley which is fixed on the mandril to one that is loose on it, by which the tread-wheel and band continue their motion while the work is examined. Thinking this simple and cheap method of obtaining his end may answer the object of Mr. Walker's inqui ries, I am, your obedient servant, T. D. L.

Railroads and Conveyance of Cattle.-Countrykilled meat will keep from thirty to forty hours longer than meat slaughtered in London; and it is allowed by the trade that many thousand pounds per annum-I think I may say two or three hundred thousand pounds-would be saved to the public and to owners, graziers, &c., if it were possible to get the beasts to market without the deterioration resulting from the driving and shameful irritation they are now subject to from dogs and drovers, One of the most eminent physicians of the day told me that he considered one-half the fevers and disorders of the inhabitants of London originated from the continued use of London-killed meat, rendered unwholesome from the state in which the animals are usually slaughtered. I look to railroads as a certain antidote to this long-continued and increasing evil; when laid down, the interest of the country butchers and graziers will be promoted by the cheapness and expedition of the conveyance, and London will have the important advantage of being supplied with meat from the country meadows, killed in a cool and healthy state, and sold at a much lower price than meat of the present unwholesome description can be obtained at, more especially at the west end of the town.-Mr. S. Munday, meatsalesman, to the Secretary of the London and Southampton Railway-Voice of Humanity, No.9.

Medical Police.-Our future annalists will doubtless record it as an historical fact, not less singular than true, that in the 19th century of refinement and civilization, at a period, too, when an appalling and inscrutable pestilence, which "walketh in darkness" and ravages the metropolis and the greater part of the kingdom-retrograding, in this respect, from the ages of Henry III. and Henry VII.-those "abodes of cruelty, filth, and pestilence," the slaughter-houses and knackers' houses existing in the midst of our densely-populated districts, still remained neither unreformed nor unremoved that during a time, too, of prevalent sickness, the wholesomeness of the animal food exposed for sale was not subjected to any inspection, but that the PUBLIC HEALTH was left wholly unprotected.-Voice of Humanity.

Blackfriars Bridge.-A Special Committee has been appointed by the Corporation of London to in

quire into the state of Blackfriars' Bridge, which has been for a long time in a very dilapidated con. dition. It is rather extraordinary that, notwithstanding the numerous reports circulated relative to the bridge, no survey has taken place since the year 1820, althought at that period it was reported to the Corporation that it was in a dangerous state.

Extraordinary Subterranean Fire.-The great heat which has prevailed, almost without interruption, for nine weeks, has produced a phenomenon in the countries bordering the lake of Geneva, to which there is no parallel on record. All at once the alarm bell of the village of Magland, in Savoy, summoned the inhabitants to extinguish a fire of a kind hitherto unheard of; for it was not houses, or trees, or heath that was burning, but the roots of the trees two feet under the ground. thing appeared on the surface, the furze and bushes were untouched, till at once several trees fell, and were then consumed by the fire that proceeded from the roots. Altogether 250 acres of fine forest were consumed. This subterranean fire is doubtless closely connected with flames which at the same time issued from the earth in several places in Lausanne. Algemeine Zeitung, Sept. 4.

No.

Progress of Steam Navigation.- In 1817 and 1818, the steam boats between New Orleans and Louisville generally occupied from 25 to 30 days in the passage, but now they perform the same voyage in 9 or 12 days, having thus increased their power more than 50 per cent.-American Journal.

Working Bees.-In a late No. of the Transactions of the Linnæan Society of Bourdeaux, a M. Espaignes affirms, that he has ascertained that the working bees are all of one sex-the male. If this be true, we shall have to look on these wonderful creatures, as miracles of civilization as well as industry.

Outside Show and Inside Comfort.-Putting a servant into a handsome Gothic cottage is like putting him into a handsome suit of livery; but there is, unfortunately, for the servant this difference, that the faults of the dwelling, if it does not fit, cannot be so readily perceived as those of the coat; and nobody may know but the occupant and his family how little comfort sometimes exists under a gay exterior. For our own part, we have seen so many ornamental cottages and lodges on gentlemen's estates, both in England and Scotland, small, damp, and badly contrived within, that we are compelled to consider them as much badges of slavery as a suit of livery. Let us hope that another generation will effectually simplify and improve the former, and entirely abolish the latter.-Mr. Loudon: Encyclopedia of Cottage, Farm, and Villa Architecture, Part IV.

INTERIM NOTICES.

Mr. Audubon's friend shall have the hearing to which he is entitled in our next.

Communications received from E. S. L.-E. H. An Engineer--Enquirer-Mr. Saul-Mr. Ashley -Mr. G. R. Booth-Saxula-C. D. S.-Mr. Young.

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, Wine-Office-court, (between 145 and 146) Fleet-street, where Communications, post paid, are requested to be addressed. Sold by G. G.BENNIS, 55, Rue Neuve, Saint Augustin, Paris, GRAY and BOWEN, Boston (U.S.)

M. SALMON, Printer, Fleet street.

402

ERICSSON'S STEAM-ENGINE AND WATERMILL.

Perhaps the most interesting problem in mechanical science is, how to simplify the steam-engine, so that its bulk and weight, which are at present somewhat enormous, may be reduced within more convenient limits without any corresponding loss of power. Owing to a variety of causes, all well ascertained by long practice, a reciprocating engine cannot be made to work to advantage at more than a moderate rate of speed; it becomes, therefore, necessary to expose the piston to a great force, (for that force multiplied by the speed, constitutes the power), and, as a necessary consequence, all the parts that have to communicate this great force, as well as the frame-work that carries those various moving parts, must be made strong in proportion. Hence it follows as a general rule, that the bulk and weight of any engine of a given power, worked by steam of given force, must depend on the speed of the piston, that is, the speed of that surface which the steam is made to propel. This truth forms the basis of the construction of the very remarkable engine which we have now to bring under the notice of our readers.

In the patent which Mr. Ericsson has taken out for this invention, he designates it as "an improved engine for communicating power for mechanical purposes;" and this generality was, perhaps necessary, since, though it promises to be of most importance in connection with steam, it may be worked by any other gaseous or fluid power, as air, water, &c. The specification describes it more particularly, as consisting of a "circular chamber, in which a cone is made to revolve on a shaft or axis by means of leaves or wings, alternately exposed to the pressure of steam; these wings or leaves being made to work through slits or openings of a circular plane, which revolves obliquely to, and is thereby kept in contact with the side of the cone.' "" But when the reader has read this description of the engine, we are afraid he will not be much the wiser for it; indeed we never before met with an engine of which it was so difficult to convey, in words,* a clear and distinct

It must be owing to this, we presume, that our contemporary, "The Repertory," has given so unintelligible, and, in many respects, so

notion, and which was at the same time so little complex in its construction. We shall, therefore, be obliged to depend more than usual on the assistance of our engraver, to make the following description plain to our readers.

The

Fig. 1 represents a longitudinal section of the engine, the circular chamber being supposed to be cut through the centre-line. AA is a circular chamber made in two parts, joined at a a, and fixed to a frame B B; this frame also supports the axis or main shaft C, to which is fixed the cone D. EE are two wings or leaves fixed to the cone; and e is a metallic segment, fitted into a groove made in the curved edge of the leaf, and pressed towards the chamber by springs in order to prevent the escape of steam. F is a circular plane, revolving on a shaft or pivot G, and supported by the main-shaft (as shown in fig. 4). oblique position of this circular plane, it will be seen, is so adjusted that its surface shall be parallel to, and in contact with, the side of the cone. His a metallic ring fitted into a groove round the cone, and divided into segments, which are pressed towards the chamber by springs, to answer the purpose of packing. I is a metallic ring for the same purpose, fitted round the circular plane. K is a cylindrical brass for the pivot G to work against e, regulated by a key k. L is a conical brass guide, kept in its place by a set-screw . M is a screwpin for giving oil to the pivot. N N are

conical brasses for the main-shaft to work in, and kept in their places by set-screws n n. oo are screw-bolts for securing the engine frame. P is a pinion or small wheel, for the purpose of communicating the power of the engine to machinery which may require a different speed. V is one of the slits or openings, in the obliquely revolving circular plane, through which the leaves work; this slit is of equal length with the leaf, and widening outwards from the surface of the plane, to accommodate the change of the angular position of the leaf, which takes place during each revolution. vv are metallic rods, kept tight against the leaf by springs, to prevent the escape of steam. WWW are thin flat arms for supporting the circular plane.

absurd an account of this engine in the No. of that Journal for the present month.

the engine, taken through the dotted line marked in fig. 2. The steam passes from the pipe Q into the circular chamber through an opening S cut through its side; this opening is of a triangular shape, and made as wide at the top as the circular plane is there distant from the base of the cone, and gradually tapering off downwards. T is the opening through which the steam escapes, and in every respect similar in construction. The dotted line U shows where the cone and the circular plane come in contact. ee are the metallic segments, already described.

Fig. 4 is a detached view of the cone in the circular plane, representing a section through their centres. It will only be necessary to observe, that d is a collar on the main-shaft, by which the cone is fixed thereto; that c is a socket-ball, working in the socket f of the circular plane; and that the dotted lines EE show the precise shape of the leaves or wings fixed to the cone.

Having thus described the nature and construction of Mr. Ericsson's engine, we

shall now proceed to explain the manner in which it is set to work. Steam being admitted into the pipe Q (see fig. 3) it passes through the opening S into the circular chamber, and being there prevented from passing the line U, where the cone and plane come in contact, it presses against the upper leaf, which, together with the cone, then revolves in the direction of the dotted arrow. Now, as soon as the said leaf gets below the top of the opening T, the steam that has been acting escapes through that opening into the pipe R, and thence into the atmosphere or into a condenser. The opposite leaf then operates in a similar manner, and so on as long as steam is admitted.

Many as have been the engines contrived for the production of rotary mo. tion, we recollect none in which that result has been obtained by such a perfect harmony of operation among the different parts. Not only the general action of this engine, but the action of every part of it is rotary. The consequence is, that it is wholly free from those serious draw