ACADEMY OF SCIENCES. 235 



pan ; ?, the length-weight ot the left arm, pan, etc.; r, the length- 

 weight of the right arm, pan, etc.; 100'\ 100'% the two weights 

 supposed to be e([ual; 1.08, 1.36, etc., the fractional additions in 

 grains to establish equilibrium. 



L. R. 



(1 ) /+100a+1.08 = j-+10{)b 



(2) /+100b — ,._(_io a-(-1.36 



(1)— (2): lOOa+1.08— 100b = lOOb—lOOa— 1.36 



lOOa = 100b— 1.22 

 ( 1 ) + ( 2 ) : 2 z'+lOOa+l.OS+lOOb = 2 r+lOOb+lQOa-fl.Se 



/ = 7-+0.14 



Whence it is determined, that the 100''' ounces-weight is 1.22 

 grains lighter than the 100'' ounces-weight; and the length-weight 

 of the left arm, pan, etc., is 0.11 grain greater than the length- 

 weight of the right arm, pan, etc. 



He then explained the means he had adopted to detect and 

 measure, in grains, the flexure of overloaded beams ; and pointed 

 out the erroneous mechanical construction of many beams supposed 

 to be " standard." 



Regular Meeting, July 1st, 1872. 

 President in the Chair. 



Eighteen members present. 



Benjamin Smith, Alexander Austin and James R. Finlayson 

 were elected resident members. 



Donations to the Library; Cal. Horticulturist, June, 1872. 

 Eng. and Mining Jour. Monograph des Poissons de Cuba, by 

 Felipe Poey. Bulletin of Essex Inst., Vol. IV, Nos. 1 and 2. 

 Illustrations of Zygenidffi and Bombycidaa of North America, by 

 Richard H. Stretch. 



Donations to the Museum : Sixteen specimens of minerals and a 

 collection of plants from the Pioche mining district, Nevada, by F. 



