the beam reffpectively, rind nre then interchanged, it wis desirable 

 to be able to transfer the pans and the weights contained in them 

 .-^om one end of the beam to the other, without opening the 

 Xldoors of the balance-case, and thus avoid sudden changes of tem- 

 ■ perature of nir in the balance-case, and consequent production of 

 {Currents of air. In order to effect this, a slender brass tube 38 

 'linches long was made to pass freely through two holes in the ends 

 '•of the balance-case, which is nearly 23 inches long, near the top of 

 "the case and half-way between the balance and the front of the case. 

 To the middle of the tube is attached a depending loop of wire. 

 Suppose that by sliding the tube the loop is brought near to the 

 right-hand end of the beam, and the pan with a weight in it trans- 

 ferred from the end of the beam to the wire loop by a brass rod* 

 » having a hook at the end, which is inserted through a hole in the 

 i! right-hand end of the balance-case. By sliding the tube in the 

 li opposite direction, the loop with the pan and weight suspended from 

 'it, is brought near to the left-hand end of the beam, to which it is 

 transferred by a brass rod having a hook at the end, passing through 

 a hole in the left-hand end of the balance-case. A similar tube half- 

 way between the balance and the back of the case, serves to transfer 

 i(the other pan and weight from one end of the beam to the other, 

 lifn this manner any number of comparisons may be made without 

 t>flbpening the balance-case, except in the middle of the series, for the 

 purpose of changing the pans. 



A sufficient number of preliminary comparisons of Sp, RS, Sb, K, 



' lEx, L, Ed having been made in 1844, the results were reduced, 



;^«when the material of one weight was platinum and that of the other 



^•brass, to what they would have been in air (^=65"66, 6=29'73), 



3or, of the mean density of the air during the comparisons of Sp and 



RS with U in 1829. Using U, Sp, RS, &c. to denote the apparent 



weights of U, RS, &c. in air (^=65*66, 6 = 2975), it was foimd 



that— jjj 1829. In 1844..^ 



RS=Sp +0-()051 RS=Sp +0-0057 



Sp =Sb +0-0022 Sp =Sb +0-0030 



RS=Sb +0-0073 RS=Sb +0-0032 



K =Sp +00420 K =Sp +0-0362 I. yd 



K =RS + 0-0369 K =RS + 0-0304 



K =Sb +0-0442 K =Sb +0-0317 



In the interval between 1829 and 1844, the difference between the 

 two platinum troy pounds Sp and RS had undergone no very sen- 

 sible relative change. If, as appears probable, Sp and RS have 

 'tindergone no sensible absolute change, Sb has gained 0*0046 grain, 

 and K has lost 0-0061 grain. Qn the same supposition it appears 



*^^*lnl824. '''''"'fnr^m. 



Ex -U= +0^010 Ex -U = +(H)099 



L -U= +0-0005 L -U = +00151 



Ed - U = - 0-0015 Ed - U = +0-0206 



D -U = +0-0022 D -.U= +0-0248 



KM-U=« +0-0021 (1829) RM-U- +0-0089 



