174 Report from the Select Committee 



The length of this pendulum is 39*13047 inches, of which the 

 yard contains 36. 



The French gGvernnient have adopted as ihe 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 meridian, whicli is engraved on the 

 platina scale preserved in the National Institute, has been com- 

 pared with the English standard yard, by Profe<;s()r Pictet of 

 Geneva, and was found to exceed it, at the temperature of 32°, 

 by 3"3702 inches ; and at the temperature of bb\ by 3"3828 

 inches. 



The standard yard may therefore be at any time ascertained, 

 by a comparison cither with an arc of tlie meridian, or the lei'gth 

 of the pcnduhini. botli of which may be considered as invarial)le. 



The standard of linear measure being thus established and 

 ascertained, the measures of capacity are easily deduced from it, 

 by determining the nuuibcr of cubical inches which they should 

 contain. The standard of weiglit must be derived from the 

 measures of capacity, by ascertaining the weight of a given bulk 

 of some substance of which the specific gravity is invariable. 

 Fortunately that substance which is most generally diffused over 

 the world, answers this condition. The specific gravity of pure 

 water has lieen found to be invariable at the same temperature ; 

 and by a very remarkable coincidence, a cubic foot of pure water 

 (or 1,728 cubical inches) at the temperature of 56|° by Fah- 

 renheit's thermometer, has been ascertained to weigh exactly 

 1,000 ounces avoirdupois, and therefore the weight of 27'64S 

 indies is equal to one pound avoirdupois. 



This circumstance forms the groundwork of all the succeeding 

 observations of your committee. 



Although in theory the standard of weight is derived from the 

 measures of capacity, yet in practice it will be found more con- 

 venient to reverse this order. 



The Vvcight of water contained by any vessel affords the best 

 measure of its capacity, and is more easily ascertained tlian the 

 number of cubical inches by gauging. 



Your committee therefore recommend that the measures of 

 capacity sliould be ascertained by the v,'eight 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 opinion, that the standard gallon, 

 from which all the other measures of capacity should be derived, 

 should be made of such a size as to contain such a weight of 

 pure water of the temperature of 56|° as should be expressed 



in 



