138 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Al'RIL 



canvas frame : " No. 7- Mr. Savary, ingineer." It had certainly at 

 one time been in some inventory, perhaps in a .sheritr'.s. An cn- 

 gravii'g was made from this portrait for my compilation, but, the 

 artist not having made a passable transcript, his copy was 

 cancelled. 



Professor Rcgaud also mentioned, that no trace of Savery having 

 been a partner with Ncwcomen is to be found in the Rolls Office. 

 Tliis may be. In a search made twelve years ago, to ascertain the 

 point, I could not find even Newcomen's patent. Perhaps I inquired 

 in the wrong quarter, in the Patent Office of Extortion. I gave, in a 

 note, Swebre'.s account, which he wrote twelve years after Savery 's 

 death. In the text I said that, " His (Savcry's) interest was con- 

 sulted by associating his name with that of Neweomen and Galley 

 in the patent." Mr. Richard Lovel Edgwortli had used the same 

 words in a letter to the editor of a periodical, in some discussion on 

 the history of the mechanism. But after all, Savery may have been 

 a sharer, as Switzcr says, in the profits, without his name appearing 

 (as I, perhaps, wrongly express it) in the patent. The date of New- 

 comen's death has not been ascertained. In 1/30, he is spoken of as 

 the " late Mr. Neweomen." Calley died two years after Savery. 

 The professor styles Savery a " military engineer." I know not 

 what that profession was in Savery's time. He assuredly was a 

 civilian. Sir Isaac Newton, who knew him, calls him "Mr. Saver}'." 

 When 1 was engaged, in 1825, in the preparation of the "Anecdotes 

 of Steam Engines," Mrs. Broughton became an object of great 

 interest. I anticipated being able, with her assistance, to get into 

 some channel of information respecting Savery, but all my enquiries 

 the7i to leai'u where she was, or if alive, were misuccessful ; every 

 trace was obliterated. 



I was highly gratified with the memoir of Mr. Trevithick in your 

 Journal for March. I believe, but I speak from an uncertain recol- 

 lection, that the late Dr. Tilloch, editor of the " Philosophical 

 Magazine," had some share in the project of sending high pressure 

 steam-engines to Peru. He lost money by his adventure, for the 

 most magnificent Spanish promises would not " take up " the small- 

 est acceptance on the silver mine-engine account, in I;ondon. Among 

 Mr. Trevithick's inventions was an elegant machine for producing 

 a reciprocating motion by a fall of water, without losing the efl'ect of 

 a single drop of the fluid ! ! He exhibited a model of his machine 

 of which I iiave a drawing. The water acted on the piston like the 

 steam on the piston of his engine. It was a kind of pet project 

 among mechanics at this period to supersede water-wheels ! Trevi- 

 thick's colum.n, a llinusand feet high, would be just the thing now in 

 Trafalgar square. It would be a worthy monument to a truly great 

 man, designed by one much greater. Some account of this, 1 doubt 

 not, would amuse your arch.itectural readers. Your correspondent, 

 who, in his memoir, has done such good and acceptable service to all 

 mechanics, must be in possession of many anecdotes concerning his 

 friend, and he will indeed do great injury to liis memory if he fail to 

 chronicle them. The slightest incident in the life of such a man as 

 Trevithick is invaluable, for his name is an historical one, and liis 

 fame is interwoven with that of the greatness of his country. 

 I am, sir, vonr most obedient servant, 



19//i Manli, 1839. " ROBERT STUART. 



THE DYNAMOMETER. 



Sir, — Having never seen an instrument of this Icind which I conceive 

 well calculated to prove the draught of a plough or road carriage in 

 a satislitctory manner, I beg leave to trouble you with a description 

 and sketch of one which I tliink might answer the purpose. 



The common Dynamometer is deficient, as it only shows the 

 strain at a particular moment, and is constantly varying during the 

 trial, so that at the end of the experiment the arerarje strain cannot 

 be calculated. To ascertain this it would be necessary during a 

 trial to note ereri/ variation indicated by the instrument and its time 

 of duration, which sometimes might amount to several, in one second 

 of time. 



Such being the case, the desideratum seems to be an instrument 

 that will s;;Hi j/^j ra owe the whole force exerted during the perform- 

 ance of a piece of work, or during a given time, at a certain rate of 

 speed. Suppose, for example, the plough to be tried, I would have 

 the instrument to show what strain was exerted in drawing a fur- 

 row from one to the other end of the ridge, taking care always to 

 note the time in which this was performed. If tried upon a carriage, 

 eitlier upon a rail or common road, lake, for instance, a mile or two, 

 at any rate of speed most convenient, llie instrument wanted is to 

 collect into one, and exhibit at one view the power expended during the 

 trial. 



My plan is as follows : — To make a strong brass tube, of any conve- 

 nient length, bored perfectly smooth within, and of such ft diameter 



as might be found to answer ; this tube to be open at the one end to 

 admit a tight-fitted piston with a polished rod, which would go through 

 a collar or small opening at the other end ; the apparatus would, 

 in fact, be a model of the cylinder, piston, and piston rod of a steam' 

 engine. The following sketch will better explain it ; the tube is 

 meant to be filled with water, which, by the draught at A, is to be 

 ejected at the small bent tube B, at a very small orifice. 



^ 



^ 



This arrangement being made, the instrument is yoked to the 

 plough or carriage at C, and the power applied at A, "the piston D 

 advances slowly towards E, forcing out the water in a very small jet 

 at B, the discharge of which will always be in proportion to the 

 strain applied at A, to overcome the resistance at C. Now, at the 

 end of any givt7i time, or given distance, the ^\ater discharged would 

 be the measure of the force exerted in drawing the carriage or 

 plough, and which of the machines in competition that perfonned 

 the work in the saine time, with the least discharge of water in a 

 given xpace, would be that of easiest draught, in other words, the 

 best plough or carriage. 



As there would necessarily be a considerable degree of friction in 

 this instrument, on account of the tightness of the piston and collar, 

 required to keep the water from escaping, it might be proper to 

 ascertain the amount of this, which could easily be done by putting 

 the instrument to a balance or steelyard when emptied of the water, 

 which would soon determine the friction in poimds. 



The strain exerted in any trial of any machine might also be 

 determined, and an average in pounds taken, by attacliing the^instru- 

 ment in the same manner when full, to a steelyard or balance, and 

 by loading it with such a weight as would cause it to discharge the 

 sa7ne (piaiiliiy of uater in the sa7nc time as was done in the experi- 

 ment with the cart or plough. The friction, as a matter of course, 

 would be to take from each to determine the positive strain. 



A scale might easily be attached to the instrument to determine 

 the exact distance the piston might move in any trial. 



There may, perhaps, be some difficulty in making the instrument 

 perfectly water tight at the piston and collar, but in my opinion a 

 slight leakage would be of little consequence as this would always 

 be in proportion to the strain to which it might be subjected, and, 

 therefore, not affect the result. 



I am not aware that such an instrument has ever been tried, 

 excepting what I have myself done, and that was upon a very small 

 scale; but I humbly think that were such an instrument perfected 

 that it would be highly useful for the proving of plough and car- 

 riages of every description, as then the merits of two competing 

 machines might be proved and determined in such a manner as to 

 prevent all cavil, being, in fact, brought to a mathematical demon- 

 stration. 



Should you think this communication worth a place in your 

 excellent journal, I may, perhaps, trouble you again. 



I am. Sir, 

 Your most obedient Servant, 



N. n. 



Roxburghshire, Scotland, Tilarch 15, 1839. 



RAILWAY CURVES. 



Sir, — Having made use of the plan recommended by "A Sub." 

 in your January number, and being convinced of its practical 

 utility, I make no apology for forwarding you a few remarks 

 upon the objections urged by your correspondent R. W. T. Your 

 correspondent's observation " that if the curvature is not equable 

 some part of it must be sharper than if the same radius were used 

 all thrcugli" is incorrect, the object being (if I understand correctly 

 the phmof " A Sub.") to begin curving'sooncr, and make the radii 

 of portions of the curve greater. I must also dissent from the asser- 

 tion that when an engine is entering upon a curve it will not be 

 afl'ected by the nature of the path it was previously describing; for 

 if this be "the case, why is the efl'ect of wear and tear of the outer 

 rail at the coMMENCiiiu'ENT of a sharp curve less when the previous 

 path is a curve in an opposite direction (forming an S) than when it 

 is a straight line? Again: Gravity acts upon a locomotive with 

 the same efifect as upon a projectile, viz., to bring it to a state of rest. 

 Now althought an engine cannot, like a cannon ball or other pro- 

 jectile, approach nearer the centre of the force acting upon it, yet, 

 prima J'acie, the vertical pressure upon the rails increases as the 



