257 



the latter purpose being determined by experiments instituted for the 

 purpose. 



The experiments 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 exceed -roVonths 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 adjusted 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 ac- 

 cident 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, toge- 

 ther with the corrections depending on the circumstances of tempe- 

 rature and pressure under which the experiments were made. As a 

 final result, it appears that one only of the gallons was ultimately 

 found in error to a greater extent than VVths of a grain, the others 

 having their errors less than a fourth of that quantity. 



The quarts and pints being next disposed of, the author describes 

 the balance contrived by him for weighing the bushels, which proved 

 so delicate as to turn with a single grain when loaded with 250 

 pounds in each scale. The resulting bushels when finally adjusted, 

 were found to have all their apparent errors less than 6'56 grains of 

 water, while the corrections for temperature and pressure only 

 amounted in some cases to no less than 138 grains ; but this depend- 

 ing on the figure of the glass used to cover them, it is not to be un- 

 derstood that the contents of the vessels have actually been ascer- 

 tained to this degree of precision. 



The adjustment of the standard yards is next described; and the 

 author concludes his paper by a summary of the results arrived at in 

 the present inquiry respecting British weights and measures. The 

 length, he remarks, of the pendulum vibrating seconds in London 

 has been found in parts of the Imperial standard yard ; so that the 

 value of the yard may at any time be known, having been referred 

 to a natural standard presumed unalterable. The length of the 

 French metre, a standard expressing a certain portion of the terres- 

 trial meridian, has also been given in parts of the English scale. The 

 weight of a cubic inch of distilled water has been determined in 

 parts of the Imperial troy pound, and thus the pound if lost may at 

 any future time be recovered. The avoirdupois pound is now for 

 the first time defined, and the measures of capacity are made to de- 

 pend on the weight of water they contain ; the Imperial gallon 

 containing ten pounds avoirdupois of water, having been declared to 

 be the unit or only standard measure of capacity, from which all 

 others are to be derived. This, it is presumed, will tend powerfully 

 to produce uniformity throughout the United Kingdom, by putting 



VOL. II. S 



