156 Scientific Notices-^Misceilaneous. [Feb. 



inent of the cube, sphere, and cylinder used by him, were 

 found to give no material variation from his results, these being 

 stated in terms of the mean of several standard weights kept at 

 the House of Commons. The troy pound nearest the mean has 

 been adopted, and declared by the legislature to be the 

 original unit of weight under the denomination of the imperial 

 standard troy pound. 



The relation between this pound and the cubic inch of distilled 

 water at 62° Fahr., bar. 30 in., has been ascertained by the 

 Commissioners of Weights and Measures, who find that the 

 latter contains 252.458 gr., each grain being the 5760th part of 

 the standard troy pound. 



The avoirdupois pound is fixed by assigning its proportion 

 to the standard troy pound, so as to contain exactly 7000 such 

 grains. 



The imperial standard gallon is defined by stating its contents 

 under the same circumstances of temperature and pressure, at 

 10 lbs. avoirdupois of distilled water, and the bushel by its 

 containing 80 such pounds. 



The author, having in compliance with a request of the Lords 

 Commissioners of His Majesty's Treasury, undertaken to super- 

 intend the construction of, and to adjust, the principal standards 

 to be deposited at the Exchequer, Guildhall, DubHn, and 

 Edinburgh ; Mr. Dollond was directed to prepare those of linear 

 measure, and Mr. Bate those of weight and measure of capacity, 

 the proper quality of metal for the latter purpose being deter- 

 mined by experiments instituted for the purpose. The expe- 

 riments for adjusting them are then given in full detail. The 

 troy pounds were first adjusted, and the exactness with which 

 this operation has been performed may be appreciated from 

 this, that the final errors of none of them exceeded 22 ten- 

 thousandths of a grain. When brought so near, it was of 

 course not thought necessary to attempt further correction. 



The avoirdupois pounds and the weights of the gallon of 

 water were then derived from the troy pounds, and finally ad- 

 justed, like them, by inclosing within the weight in hollows left 

 for the purpose, wires equal to the errors ascertained to exist in 

 them. The weights of these wires in each case is stated, so 

 that should they by any accident be taken out and lost, they 

 may be restored. 



He next describes the method used in adjusting the gallon 

 itself, the method of filling it exactly, and of weighing it when 

 filled, together with the corrections depending on the circum- 

 stances of temperature and pressure under which the experi- 

 ments were made. As a final result, it appears that one only of 

 the gallons was ultimately found in error to a greater extent than 

 six-tenths of a grain, the others having their errors less than a 

 fourth of that quantity. 



