88 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[March, 



Accordingly, the connecting roil is always made as long as may be, 

 within limits fixed by other circumstances, for thereby the oliliquity of 

 its action is diminished. A method of communicating the motion of 

 the j)iston to the crank, without loss of power by such a cause, has 

 therefore been a (hsidiiatnin. 



The fundamental princiiile of my contrivance is, that the epicycloid 

 generated by any point of the circumference of a circle rolling on the 

 interior of tlie circumference of another circle of twice its diameter, 

 is a straight line, tlie same point always describing the same straight 

 line. Tluis, the circle A B F, fig. 1, rolling on the circle AC A', in 

 the above-mentioned circumstances, any point, A in it, moves up and 

 down A A', a diameter of the larger circle, It is easily inferred too, 

 that the centre E, of the inner circle describes a circle EG, of equal 

 radius concentric with the larger circle ; so tliat, were E and F con- 

 nected, the connection E F would move round F, in the manner of a 

 crank. 



Now, let A A' and A F, fig. 2, be tlie primitive diameters of two 

 teethed wheels, in which the teeth of the larger one on the interior of 

 the circumference, and those of the smaller on its exterior, so that they 

 may run into each other. Let G be the extremity of a shaft concen- 

 tric with the wheel A A', and carrying a crank GE, of which the pin 

 at E is also concentric with the smidler wheel A F. Then, when G 

 revolves, it carries the wheel A F with it, which runs on the crank |)in, 

 its teeth at the same time taking into those of the wheel A A', and 

 the point A of the wheel A F describing the path A A'. Reversing 

 the mode of action, suppose the large wheel to be fixed ; then if the 

 piston rod of a steam cylinder of which the stroke is eciual to A A', be 

 jointed to a pin standing on the primitive circumference of A F at A, 

 for example, the machine, with a fly on the shaft G, will work, so as 

 that this shaft will have a continous rotatory motion. 



In this method there is neither connecting rod nor parallel motion. 

 The ))iston rod is connected immediately with the pin on the wheel 

 A F, and is led up and down rectiliueally by the very nature of the mo- 

 tions. 



Now, the fact that no special parallel motion is recpured, proves 

 that none of the power is wastefully exerted. To be more minute, 

 however, suppose the crank in the position F E', fig. 2, A' A" will be 

 the ])iston rod, jointed at A" to the wheel. Producing F E to B, this 

 will be the touching point of the two circles. Draw A" B, A"E', and 

 drop the perpendicular E'C upon A" B. Then A" E' B must he con- 

 sidered as a crooked lever of the second kind, in which B is the ful- 

 crum, and E' and A" respectively, the points of application of the 

 resistance and power. Now, in the triangles F E' A'', A" E' B, the 

 angle E' F A"+E' A" F (or 2 E' A" F, 5. 1. Euclid) =2 right angles— 

 F E' A"; and E' A" B + E' B A" (or 2 E' A" B, 5.1. Euclid)=2 right 

 angles— A" E' B (32. 1. Euclid). And taking the half sum of these 

 ccpiations, we have E A F+E A B =2 right angles— (F E' A"-|- A" E" B) 

 = 1 right angle, that is. A" B is perpendicular to A' A'', and therefore, 

 A" B is the leverage of the power acing in the line A' A''. C B is 

 also the leverage of the resistance acting in the line E' C ; and it is 

 easily seen that A B=2 C B ; so that, as this demonstration applies in 

 every position of the crank, putting the angle A" F B' = Z, and FB = 

 1, we conclude, in general, that, 



1. The leverage of the power =sin. Z ; 



sin. Z 



2. resistance = — — \ 



3. The line of action on the crank is always parallel to the piston 

 lod. Now, as could easily be proved, by this mode of action, namely, 

 the parallelism of the impulse on the crank, the whole power of the 

 piston is communicated to the main shaft ; and thus is my object 

 proved to be attained. 



Besides the advantage already stated, this engine possesses two 

 Others, simplicity of construction, anJ smaliness of bv>lki It differs 



from the common ones in this also, tliat with the same sweep of crank, 

 it has twiiu> the length of stroke; and accordingly, as we see from the 

 above two fixed conclusions, the leverage of the power is twice that 

 of the resistance. 



I am, Sir, your obliged servant, 



Daniel Clark. 

 Glasgnw, Dec. 19, 1S39. 



HOOPER'S POST OFFICE LETTER WEIGHTS. 



The accompanying engraving represents one of Hooper's peculiar 

 letter balances, the merits of which are its simplicity and accuracy ; a 

 grain in ert'ect would turn the balance either way. Although numerous 

 devices have been inlreduced for this purpose, none that we have 

 seen surpass this in utility, in which it is as much before its compe- 

 titors, as it was in priority of introiluction, 



TilK FITZWILLIAM MU.SF,UAf. 



TiiF. FitzwiUiam Syndicate have reported to the Simatc : 



" That Mr. Easevi has corliliea to the Vicc-Clianci'Uov that Mr. Baker has 

 cxcculeil works in tlie IjiiililiuH of the FitzwiUiam Museum to the value of 

 £34,00(J or thereabouts ; and Mr. Basevi has tliereuiuin retommended that a 

 sum of £5.000 be now paid to Mr. liaker on ncciiuiit of tlie saul works in ail- 

 dilion to the sum of £25,500 already paid to liim on that account. 



" Tliat although the above-mentioned sum of £5,000 exceeds the instalment 

 which Mr. Baker is at present entitled to demand according to the terms of 

 the contract; the .Syndics, under the cireumsttuires stated in 'Mr. Basevi 's 

 certificate and letter, bcL' leave to recommend to tlie .Senate that the Siiid 

 sum be paid to Mr. Baker, provided Ibat be is willing to agree .'hat the 

 balance to he retained by the Vice-t'hancellor until six months alter Mr. 

 Basevi shall have duly certified the entire cimipletiun of the works, shall ae- 

 coiding to the terms" of the enntiaet, bu not less than 10 per cent, upon the 

 w hole amount of the contract ; and that Mr. Baker's sureties are willing to 

 agree thiit the payment of the sum of £5,000, as above proposed, shall not 

 atlect or imiiair their present liability under the contract." 



The .Syndics further recommend ; 



" That Mr. Basevi be authorized to order the execution at a cost not ex- 

 ceeding £1,000, of certain works at the FitzwiUiam Museum not included in 

 Mr. Baker's contract ; it being advisable that such works should be completed 

 previously to making any further contracts for the linishing of the building. 

 R. T.VTHAM, I'icc-Clmncellor. 



\V. French. O- Peacock. 



G. AirosLuc. J. H.vvii.ANn. ^ 



J. Graham. H. PHii.Port." 



At the Congregation this day, a Grace will be oftcred to the Senate to 

 confirm the above Report. 



■ Mr. Basevi's certificatg and Utter will be laid on the Registrar's table,— 

 CmnbrUlge Advertiser, 



