COMPENSATION CURB. 21 



you will immediately afceftain towards what part of flie circles Defcripiion of a 

 you muft (hift V. If you find its rate flow with iieat, you H'^^^''^^'''''' 

 muft fliift V to lengthen your circles, and if faft, the contrary ; 

 and by marking your circles each lime you have occafion to 

 fliift V, yon will be enabled to adjufl: the curb to the exa6l 

 cxpaniion required. W is a loofe piece of fteel, which fits 

 in the notch of V between the two exnanfion circles, to keep 

 them faft in their proper pofitions when fcrewed by F. S S 

 are two fteady pins made faft in the frame-plate, which re- 

 ceive. the circle E between them to prevent the a61ion of P, 

 the regulating fpring, from affecting C, the curb, by moving 

 it to or from the center during the going of the watch, Tiie 

 two expanfion circles require to be made very delicate; it is ^ 



therefore to be obferved by the manufadurerof this inftrument, 

 that the brafs in each circle is to be the thicknefs of the fteel ; 

 fo that when the two bodies are foldered together, they will 

 make two thicknelfes of the edge of a main-(pring of a watch. 

 The larger your watch will admit the diameter of the curb> 

 the better, ft muft be at leaft the fize of the balance. 



Letter from Mr. Bo swell, in Anfzver to An Old Corre- 

 spondent. 



To Mr. NICHOLSON. 



SIR, Jpril 10, 1805. 



JL HE perfon figning j/owr Old Correfpondenty has thrown fome Mr. Bofweli 

 very undeferved retiedions on my laft communication in your J!'"'^'"-^^ "l" 

 Journal. dence. 



In anfwer to his remarks, I beg leave to obferve that the 

 introdudtion to my paper contains fufficient to juftify me fully 

 from his imputations. 



I have there afTerted no more than that ** I have difcovered 

 ** a method of coming fo near the truths that fliould it turn 

 *' out to be in reality notfo exad as appears to me, yet it pro- ' 

 *' mifes to be fo ufcful for common computations that I am 

 ** induced to fend it for publication, ij you approve of it.*' 



I know 



