MODE OF ATTACHING A FRESH CARRIAGE TO A RAILWAY TRAIN, ETC. 133 unprofitable indeed must be our specu- I am, Sir, yours respectfully, London, Nov. 21, 1838. SMOKE-CONSUMING STOVE. Sir, I inclose you an extract from the Engineers and Mechanics' Cyclopædia, by which "Junius Redivivus" will perceive that he has been forestalled in his proposal to make the two side jambs of stoves a repository for coals, for the purpose of effecting the combustion of the smoke. Were the facts stated not beyond all question, still I am sure his natural gallantry would not allow him to dispute the invention with a lady. It is stated in the description, that the hobs or lids "should shut down closely; if air-tight the better." Now, it would be altogether impossible to make them do so; and in that case the gas, smoke, &c., would escape unconsumed into the chimney, and a loss, instead of economy of fuel, would result. This might be prevented by using a luting; but it would be so frequently required to be renewed, that this is quite out of the question. It appears to me, that by making the side of the stove between the fire and I am, Sir, yours respectfully, London, Nov. 20, 1838. "A plan of a stove designed for burning its own smoke, was communicated by Mrs. Rachel Smith to a periodical journal, which seems susceptible, by its simplicity of construction and soundness of principle, to be made effective for the object intended. The stove is made exteriorly of the usual form, excepting that the fire-part, f, is of greater length, or height than is common, and the spaces under the hobs are made into reservoirs to receive the coals, as shown at C C, for supplying the fire. The hobs are upon hinges, and form lids, which shut down very closely; if air-tight the better. The cheeks of the grate are open at the bottom, so that the coals lying upon the inclined planes of the reservoirs descend by their own weight, and occupy the lower part of the grate; as the fuel is consumed, or raised by the poker, a fresh portion of coals enters from either or both of the reservoirs, and fills up the space. In this manner the fuel is constantly supplied, occasioning little or no smoke. The reservoirs should be of sufficient capacity to hold enough coal for the day's consumption." MODE OF ATTACHING A FRESH CARRIAGE TO A RAILWAY TRAIN WITHOUT STOPPING THE TRAIN. Sir,-The delay and inconvenience, the wear and tear of machinery, which arise from frequent stoppages, as well as the advantages both to proprietors and travellers, which a solution of the problem above stated would afford, are all L 40 = ly; abundance of time for communicating motion to the new carriage (C). If the last carriage (L) be furnished with several coils of spring, as many must be put in gear as are thought necessary, according to the weight of C. Let C be placed near the rails, and as becomes attached to L passes the rope C, and begins to run out; it remains to get C upon the rails as soon as possible after L has passed. This may be done in various ways. 1st way: Let C be placed on a frame parellel to the rails, and be set on the rails by a strong spring, which L releases in passing, and by a motion perpendicular to that of the train. By this way, however, at least 1" of time is lost. 2nd way: Let C be placed on a side rail slightly curved and leading into the railroad, then motion commences the instant L passes, and this motion may be aided by a strong spring released by L and propelling C; or (which might be still better) by a tube containing compressed air. EB, Fig. 2, the rail (slightly curved) down which C descends. A portion, H B, of this rail is moveable about a hinge H, and can be raised into the position H K, so as to allow the wheels of the trains to pass under it. The instant L passes B, KH falls, or is set in the position H B. The instant H B is so set, C reaches H, and begins to descend down HB. This will be effected by a trigger, at I, released by L, and having its distance from A properly adjusted. If, then, the height of E, from which C begins its descent be properly assumed (allowing for friction, &c.) C may be made to arrive at B with a velocity greater than that of the train. C will then overtake the train, and by a simple device become attached to it. This method has the advantage of being very simple, and in deep cuttings the necessary apparatus would be erected at a small expense. On plain ground, and where land can be easily obtained, the tractrix would probably be preferable. MR. WHITE'S QUESTION IN SURVEYING. parallel to A B, and a small horizontal wheel, or by having another carriage on the other side the rails attached at the same instant with C. If C were suffered to move freely, it would describe a well known curve called the tractrix. Experience would soon decide whether a slight modification of this curve or the quadrant would answer best in practice. The latter would require the axles of C to converge to O. Áspring might be released, which should set them parallel the instant C came upon the straight rails, A B, FE. Cambridge, June 28, 1838. G. R. MR.WHITE'S QUESTION IN SURVEYING. Sir, I return "O.N." my best thanks for the simple directions he has given me for solving the trigonometrical question which I proposed in your highly useful Journal (No. 760): I found it quite an easy task to make out an arithmetical solution from "O. N."'s rules. I was somewhat surprised to find that the said question had attracted the notice of a gentleman at the Cape of Good Hope, who has given a geometrical construction, and an analytical solution of it, in the South African Commercial Advertiser for June 27th.* I have made out an arithmetical solution of it from his investigations, and I find the required answer exactly agrees with that which I obtained from "O. N."'s method. the gentleman at the Cape of Good Hope considers the question, and all others of a similar nature, of very high importance in trigonometrical surveying : such being the case, Mr. Editor, perhaps you will republish his solution in your scientific Journal. As "To the Editor of the South African Advertiser." "Sir,-In turning over the leaves of a late number of the Mechanics' Magazine, my attention was drawn to the following notice addressed to the editor of that periodical." [Here Mr. White's letter is quoted, which, of course, we need not repeat.] "This is one of a numerous and interesting class of questions connected with the subject of trigonometrical surveying, which are all reducible to the well-known * We also have received a copy of this newspaper from a correspondent in Africa.-ED. M. M. 137 problem originally proposed by Townley; by which, from three objects given in position, and the angles which their mutual distances subtend at a station in the same plane, the relative position of the station is determined. They are all of practical importance, both to the military and land surveyor; and in this colony especially, where in the Survey of Grants every point of importance ought to be determined by triangulation, they should find a place in the note-book of every surveyor. With the view of drawing the attention of our colonial surveyors to the subject, I am induced to request the favour of a corner in your next paper, for the following solution of the above question. 66 Yours, &c. I. At H, in the known distance WH, lay off the angles WHQ, WHR respectively equal to the given angles WSC, WCS; and in like manner at W, the angles HWQ, HWR equal to the given angles CS H, SCH. Draw Q R. R Through the points W, Q, H, describe a circle intersecting QR in S; and through the points W, R, H, describe another, cutting the same line in C. By this construction, the position of S and C, where the angles were observed, are determined. Join SH, CH, and on SC describe the triangle S PC, having the angles at |