90 



as the volume of the lost standard remains unknown, the weight of 

 the air displaced by it, and, consequently, its absolute weight, is 

 uncertain within limits far exceeding the errors of weighing. 



Let U denote the lost standard; Ex, L, Ed, D, RM the troy 

 pounds of the Exchequer, the cities of London, Edinburgh, Dublin, 

 and the Royal Mint, respectively ; Sb, K two brass troy pounds, Sp 

 a platinum troy pound, all in the custody of Professor Schumacher ; 

 RS the platinum troy pound of the Royal Society. Let A prefixed 

 to the symbol by which any weight is designated denote the ratio of 

 the density of the weight at the freezing-point to the maximum den- 

 sity of water ; t the temperature of the air in degrees of Fahrenheit's 

 scale ; b the height of the mercury in the barometer in inches re- 

 duced to the freezing-point. The symbol t placed between the 

 symbols of two weights will be used to denote that they appear to 

 be equal when weighed in air. The two weights in this case will 

 not be equal unless their volumes are equal. When the weighings 

 have been made in air of given density, or have been reduced to what 

 they would have been in air of given density ; or, when the volumes 

 of the weights, the temperatures and pressures of the air being un- 

 known, we are compelled to assume that their volumes are equal, 

 the symbol = may be substituted for s . 



By the observations of Captain Kater (Philosophical Transactions, 

 1826), 



Ex =U + 0-0010 



L =U+0-0005 



Ed =U.+ 0-0015 



D = U + 0-0022 



RM=U+0-0021 

 By the observations of Captain v. Nehus in 1829 



No. ofobs. b. t. 



300 Sp :U-0-00857 29'722 65-62 

 140 RS ^U-0-00205 29*806 6573 

 60 Sb :U-0-01034 29'965 64-50 

 92 K ^U + 0-03389 29'646 65-09 

 16 RM^U + 0-00887 29-679 65-91 

 10-log A Sp=8-67392, 10-log A RS=8'67392, 

 10-log A Sb=9'08471, 10-log A K=9'09724. 



