THE ART OF WEIGniNG AND MEA.'^UKING. 



623 



will be to regard the entire set as a standard of 5115 troy ounces. In 

 that case the summation of the several columns gives 



512 ounces = 128 x -|- 'W grains. 



■whence 



X = 4 ounces — 0.3047 grain (2) 



and by substituting that value in the equations (1) we obtain the cor- 

 rections to the several weights given in the second column of Table I. 



Table I.— Corrections to the Exchequer Standard Troy Weights of 1588, 

 Derived from the Weighings made by Messrs. Harris and Chisholm. 



From equations (1) and (2) we have 



4 ounces = 4-oz. weight + 0.5547 grain. 

 8 ounces = 8-oz. weight -j- 0.3594 grain. 



whence it follows that the sum of the 8 and 4 ounce weights, which 

 constituted the Exchequer standard troy pound, was too light by 

 0.9141 of a grain. As the mean correction obtained from the four 

 weights belonging respectively to the Mint and to Mr. Freeman, agrees 

 closely with this result, the true correction to the Exchequer standard 

 must have been very approximataly 1 grain ; and in adopting 1| 

 grains the committee seem to have augmented the weight of the troy 

 pound by about one-quarter of a grain. The corrections which result 

 to the Exchequer troy weights upon the committee's assumption that 

 the sum of the S and 4 ounce weights was IJ grains too light are given 

 in the third column of Table I ; while the fourth column contains the 

 corrections found by Mr. Ciiisholm in 1873,* and the fifth column shows 

 the loss of weight which occurred between 1758 and 1873. In view of 

 the fact that these weights were constantly used for comparing local 

 standards during a period.of no less than two hundred and thirty seven 

 years, from 158S to 1825, their excellent preservation is very remarkable. 

 In the report of the committee of 1758 there is another set of com- 

 parisons of the Exchequer troy weights,! said comparisons having 

 been made on April L4, 1758, in accordance with the directions of 



»50, p. 21. 



1 13, p. 435. 



