STATE PAPERS. 



359 



Koyal Society, and Professor Play- 

 iair of Edinburgh. 



From the evidence of these 

 gentlemen, it appears that the 

 lengtli of a pendulum making a 

 certain number of vibrations in a 

 given portion of time, will always 

 be the same in the same latitude ; 

 jind that the standard English yard 

 has been accurately compared with 

 the length of the pendulum which 

 vibrates 60 times in a minute iu 

 the latitude of London. 



The length of this pendulum is 

 39.13047 inches of which the 

 yard contains 36. Any expert 

 watch-maker can easily adjust a 

 pendulum, which shall vibrate ex- 

 actly 60 times iu a minute. 



The French government have 

 adopted as the standard of their 

 measures, a portion of an arc of 

 the. meridian, which was accu- 

 rately measured. The standard 

 metre, which is the 10,000,000th 

 part of the quadrant of the meri- 

 dian, which is engraved on the 

 Platina scale preserved in the Na- 

 tional Institute, has been com- 

 pared with the English standard 

 yard, by Professor Pictet of Ge- 

 neva, and was found to exceed it, 

 at the temperature of 32 degrees, 

 by 3.3702 inches; and at the 

 temperature of 55 degrees, by 

 3.3828 inches. 



The standard yard may there- 

 fore be at any time ascertained, 

 by a comparison either with an 

 arc of the meridian, or the length 

 of the pendulum, both of which 

 may be considered as invariable. 



The standard of linear measure 

 being thus established and ascer- 

 tained, the measures of capacity 

 are easily deduced from it, by de- 

 termining the number of cubical 

 inches which they should contain. 



The standard of weight must be 

 derived from the measures of ca- 

 pacity, by ascertaining the weight 

 of a given bulk of some substance 

 of which the specific gravity is 

 invariable. Fortunately that sub- 

 stance which is most generally 

 diffused over the world answers 

 this condition. The specific gra- 

 vity of pure water has been found 

 to be invariable at the same tem- 

 perature : and by a very remarka- 

 ble coincidence, a cubit foot of 

 pure water (or 1,728 cubical 

 inches) at the temperature of 56|* 

 by Fahrenheit's thermometer, has 

 been ascertained to weigh exactly 

 1,000 ounces avoirdupois, and 

 therefore the weight of 27,648 

 inches is equal to one pound 

 avoirdupois. 



This circumstance forms the 

 goundwork of all the succeeding 

 observations of your Committee. 



Although in theory the standard 

 of weight is derived from the 

 measures of capacity, yet in prac- 

 tice it will be found more con- 

 venient to reverse this order. 



The weight of water contained 

 by any vessel, affords the best 

 measure of its capacity, and is 

 more easily ascertained than the 

 number of cubical inches by gaug- 

 ing. 



Your Committee therefore re- 

 commend that the measures of 

 cai)acity should be ascertained by 

 the weight of pure or distilled 

 water contained by them, rather 

 than by the number of cubical 

 inches, as recommended in the 

 4th resolution of the Committee 

 of 1758. 



Your Committee are also of opi- 

 nion, that the standard gallon, 

 from which all the other measures 

 of capacity should be derived. 



