I first put a piece of linen or calico over the board, and plaster the cement upon it half an inch in thickness: the use of the linen is, that the whole may be easily separated at once from the cover,whenever a glass or other hive is required to be added above. My flat hives are always placed under a boarded house or shed, and my stands are entirely unconnected with each other. A large garden flower-pot, whose sides are more upright than those usually made, forms a good stand for each hive; the upper edge should be perfectly level, and the interior filled with sand, with a small quantity of oak sawdust or salt sprinkled over it, to exclude insects. No mice can climb the sides of this stand, and its being moveable adds much to its convenience. The cement I have spoken of is composed of two-thirds of fresh cow-dung, and one of sifted woodashes, which, if placed in a wheelbarrow, may be quickly beaten into a uniform mass, and, being put into some covered vessel, will keep many months ready for use. For common purposes, the fresh cowdung collected from the fields may be used; but if the cement is to be exposed to the weather, that collected from cows or oxen fed in stalls, on dry food, is preferable, it being more tenacious. I am, Sir, CORRESPONDENCE. A Correspondent, "desirous of promoting the arts, &c. suggests the pro priety of using Plates of Zinc for the casing of such Mill-stones as are used for grinding wheat, and will thank any of our Correspondents to inform the public, through our medium, where such plates as are proper for that purpose may be procured-say, of about 1-12th of an inch thick, 16 inches broad, and 4, 5, or 6 feet long." The Newspapers make mention of a Time-piece, brought to perfection by a Gentleman at Cambridge, composed only of one wheel and a lever, and put in motion by a chemical process. An old Correspondent would be obliged to any of our Correspondents for a description of it. Chemico-Mechanicus thinks, that the ingenious contrivance for throwing a self-regulated stream of hydrogen gas upon spongy platina, of which a draught Numbers, might be applied to the putand description are given in one of our ting in motion a time-piece. H. N. says, that "perhaps P. L. M. (No. 104) will find Simpson's Treatise on Fluxions, lately re-edited, in two vols. 8vo., by a Graduate of Cambridge, the best suited to his purpose." "P. L. M.” he adds, "is no doubt aware, that at least a general acquaintance with the pure and several branches of mixed mathematics is first six books of Euclid, the working of a necessary pre-requisite; such as the Algebraic Equations, Conic Sections, and Mechanics. With those preparations he will no doubt be able to follow the author, generally speaking; but he must not be deterred if occasionally he encounter difficulties, which can only be removed by reference to some one more advanced in the science." Advertisements for the Covers of the Monthly Parts must be sent to the Publishers before the 20th of each month. Communications (post paid) to be addressed to the Editor, at the Publishers', KNIGHT and LACEY, 55, Paternoster-row, London. Printed by, MILLS, JOWETT, and MILLS (late BENSLEY), Bolt-court, Fleet-street. 370 IMPROVEMENT ON THE HIGH PRESSURE STEAM-ENGINE. IMPROVEMENT ON THE HIGH PRESSURE STEAM-ENGINE. BY MR. JOHN PATTISON. [To the Editor of the Mechanics' Magazine.] any The Steam-Engine, in its present various and modified applications, is connected with so very large and important a part of the wealth and commerce of our country, that attempt to render it more simple in its construction, or more effectual in its operations, can need no other apology than its proportionate consequence to the wants and happiness of mankind. idea was practicable, and, to a certain extent, beneficial, With this opinion I mentioned the subject to Mr. Buddle, who thought it was at least worth trying, and with his usual liberality, and that constant encouragement which he always affords to the improvement of science, requested me to inake an experiment, the latter end of last year, on the pumping engine at Elswick Colliery. The cylinder of this engine is 314 inches diameter, the piston making seven 8 feet strokes per minute, and delivering at each stroke 64 gallons from a depth of 55 fathoms. Previous to inaking this experiment, the safety valves on the boiler were loaded at 34.7 pounds per inch, and the boiler consuming 69 cwt. of coals in eight hours and a half. After I completed and set to work the condenser, and attached a pump My business of life, hitherto, has from the hot well to feed the boiler been the erection and management (the engine going at the same rate, of steam-engines, as they are used and performing the like quantity of by the coal trade in the neighbour work in the same time), the pressure hood of Newcastle, where the Trevion the boiler was reduced to 27 thick or high pressure engine has been lately introduced at several of pounds per inch, and consuming only the collieries, for the purposes of 41 cwt. of coals in the eight hours half. Nothing could be more pumping water and drawing coals. satisfactory than this result, and, to Some of those engines, so applied, have been under my management for prove the nature and extent of the some time, during which it has fre- vacuum, I attached a mercurial barometer to the condenser, and quently occurred to me, that, instead found it sustained a column of merof discharging the steam into the atmosphere, a considerable increase altitude, its greatest height being cury upon an average of 14 inches of power might be gained by open- about 22 inches. ing the discharging valves into a close vessel, and throwing in at the same time a jet of cold water, so as to produce, to a certain extent, a vacuum, which, of course, would so far assist the alternate sides of the piston, and be a proportionate real increase of power. Undoubtedly the difficulty of getting quit of the air generated by condensation, without the use of an air-pump, presented itself, and to some of my friends, to whom I mentioned the subject, seemed an insurmountable obstacle; but some experiments which I had made on what is termed high pressed steam, together with my observations of the way in which the common atmospheric engine clears the cylinder of air, confirmed me that my and a Since carrying this into effect, I have attached a double condenser to a machine for drawing coals, which is bringing to bank five score carves or baskets in an hour, from a depth of 66 fathoms, drawing two at a time. The result of this is equally satisfactory with the other, in having fully as much lessened the pressure per inch on the boilers, and considerably diminished the consumption of coals. I have prefixed a drawing of a single condenser, as attached to a pumping engine. To those who are acquainted with the action of a Bolton and Watt's engine, any description beyond a reference will be unnecessary, and, SPHERICAL CHAMBER CANNON. as the condensing part is so exceed ingly simple, it will need little explanation even to those who have not attended to this part of the steam-engine. Like Mr. Watt's condenser, this one requires blowing through previous to starting; but, in order to produce here the maximum effect, the injection must be so regulated as not to cool the condenser below the temperature at which the shifting valve will be lifted once every double stroke. In the pumping engine above-mentioned, the quantity of cold water used for condensing each alternate stroke is 2.75 gallons, from a jack-head cistern 22 feet above the condenser. The upper discharging valve, and the one for the injection, are both lifted at the same time, but the bottom discharging valve is opened into the condenser a little before the injection, which, of course, lifts the shifting valve, expelling the air previously contained, at the same instant the injection is thrown in, when a vacuum is produced of not less than 22 inches of mercury. It will easily be seen that the injection water, together with the condensed steam, pass down the sink pipe, and are discharged at the foot valve at the same time the air is expelled. This valve is kept in its seat by a weight and lever, which is nearly equipoised, and which readily admits the discharge of the water into the hot well. 371 SPHERICAL CHAMBER CANNON. J. Walkinshaw appears to claim, for his brother, the invention of the I remain, Sir, From what I have stated it will, perhaps, be objected by some, that the vacuum is not constant and uniform; this, indeed, must necessarily be the case from the manner in which the air is expelled from the condenser, but, as far as regards its action on the engine, it is not productive of the least irregularity, but, on the contrary, is a real and September 12th, 1825. permanent increase of power, on the lowest estimation, of seven pounds per inch, and that too without the drawback of any additional machinery beyond raising the injection water and lifting the valve. I trust it will be fully understood that I am not claiming any new in Charlotte-street, "Artillery, Chap. II. Section 8th. "It is evident that the greater the quantity of powder which takes fire at the same instant, the greater its effect will be upon the ball. This gave rise, towards the end of the last 372 LONDON MECHANICS' INSTITUTION. century (the 17th), to a new construction of the bore of cannon, by making a cavity, in the form of a sphere, a little flatted," &c. "The design of this contrivance was to throw a bullet from a piece, shorter, lighter, and more easy of carriage than others, with the same degree of force as from those before used. Experience proved that the construction of these pieces answered the end proposed," &c. But, as it was difficult to clean the chamber after the piece had been fired, there frequently remained some sparks behind, so that, when it was necessary to fire the pieces as fast as possible, many cannoneers had their arms blown off as they were charging them; and, besides, as the powder, before it forced itself out of the chamber, pressed on all sides with such violence and impetuosity, in a very little time the carriages were broken to pieces and rendered unserviceable; also, by a frequent repetition of this violent agitation, the piece acquired a very considerable recoil, and the direction of the ball became uncertain. For these reasons this contrivance was entirely laid aside," &c. LONDON MECHANICS' INSTITUTION. On Wednesday, the 7th inst. the seventh Quarterly Meeting of this Institution was held at their Theatre in Southampton-buildings; the President, Dr. Birkbeck, in the Chair. A Report of the Committee of Management was read, from which it appeared, that the progress of the Institution has been such as to exceed the most sanguine expectations of its friends and supporters. Five hundred and twenty-five new members were added during the last quarter, making the whole number at present 1483. A considerable number of the members receive instruction in the schools of arithmetic, mathematics, drawing, and French, and their great attention has been amply rewarded by a rapid progress towards proficiency. The philosophical and mechanical apparatus has been greatly increased, and the library so extended by liberal donations and extensive purchases, that in the course of the ensuing month the Committee will be able to establish a circulating library for the use of all the members. The Report concluded by congratulating the members on the bright prospect of the realization of the highest hopes they could have formed of the success of the Institution, and on the zeal, activity, and harmony, by which all their proceedings were characterized. Mr. Cope, Secretary of the Building Committee, read a Report, by which it appeared that the theatre cost 3700/., the whole of which was advanced by Dr. Birkbeck, and that 11707. had been expended on other buildings and improvements. One of the auditors read a Report of the state of the accounts of the Institution, by which it appeared that their finances are in a most flourishing condition, there being a balance of upwards of 10007. in their banker's hands. All the Reports were agreed to. Thanks were voted to all the officers of the Institution. On thanks being voted to Dr. Birkbeck, which was followed with the greatest applause, that gentleman, in making his acknowledgments, observed, that the example of the London Mechanics' Institution had excited such a desire for a participation in the blessings it was calculated to impart, all over the country, that the most gratifying accountswere constantly receiving of the formation of new Institutions; and it must be delightful to every friend of human improvement and happiness to find, that their establishment was uniformly attended with increased order in conduct, and respectability in character; confirming in every respect the opinion formed, by those who had assisted in the establishment of the London Institution, of their important results and extensive utility.Circular to the Newspapers. |