542 Royal Society .— 



.following weights : — The brass troy pounds of the Exchequer Office ; 

 the brass troy pounds from the cities of London, Edinburgh and 

 Dublin; the platinum troy pound and the two brass troy pounds 

 then in the possession of Professor Schumacher ; the platinum troy 

 pound of the Royal Society ; the troy pound used by the late 

 Mr. Robinson of Devonshire Street, purchased by the Committee ; 

 four troy pounds made in 1 7o8, two of which were formerly in the 

 possession of Mr. Bingley of the Royal Mint, one the property of 

 Messrs. Vandorae and Titford, and one the property of the Bank of 

 England. 



The troy pounds of the Exchequer, and of the cities of London, 

 Edinburgh and Dublin had been compared with the lost standard by 

 Captain Kater in 1824. The three troy pounds in the custody of 

 Professor Schumacher, and the troy pound of the Royal Society, 

 were compared with the lost standard with extraordinary care in 

 1829 by the late Captain v. Nehus. The troy pounds bearing the 

 date 1758 were constructed, along with the lost standard, by 

 Mr. Harris, Assay Master of the Mint. These were referred to at 

 the suggestion of Professor Schumacher, in the hope of arriving at a 

 knowledge of the volume of the lost standard, which, unfortunately, 

 had never been determined by weighing it in water. For, as long 

 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 ^ 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 

 hot 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 and the temperatures and pressures of the air being 

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

 the symbol == may be substituted for ii . 



By the observations of Captain Kater (Philosophical Transactions, 

 1826),— 



Ex =U-f 0-0010 



L =U4-00005 



Ed =U-|-0-0015 



D =U-i-0-0022 



RM=U-f.00021 



By the obser\'ations of Captain v. Nehus in 1829-^ 



