68 Dr. Moll on the Comparison of 



the other at the observatory, will be of unequal weight with a 

 correct brass kilogramme weighed in air *. 



The result of all these experiments is, that we discover 

 differences between weights, which ought to have been equal, 

 which altogether appear intolerable, and there remains an 

 obscurity about the real value of these weights, which it is 

 difficult to account for. Yet, if we are to look to the compa- 

 rative weights of the kilogramme, and the British troy pound, 

 as deduced, not by actual weighing, but by computation, we 

 shall find differences still greater and more bewildering. 



1st. In 1769, Tillet, the French academician, determined, 

 by actual weighing, the relation of the British troy pound and 

 French poids de marc f; hence by the known proportion of this 

 poids de marc to the kilogramme, as determined by Lefevre 

 Gineau, we may compute the value of the kilogramme in 

 British troy grains. 



2nd. In Dr. Young's Lectures on * Natural Philosophy/ is 

 a calculation of the comparative weight of the kilogramme 

 and British troy, from the known ratio of the metre and 

 British yards, and the experiments of M. Lefevre Gineau 

 and Sir George Shuckburgh on the weight of a cubic decime- 

 ter and a British inch of water at a certain temperature J. 



3rd. In the Appendix to the third report of the British 

 commissioners for weights and measures, the result is given of 

 a similar computation drawn from the same source and the 

 repetition of Sir George Shuckburgh' s experiments by Captain 

 Kater. 



4th. Mr. Mathieu of the Paris Observatory, computed from 

 French and English experiments the value of the kilogramme 

 in British troy grains ||. 



From all these operations the following different relations 

 of the kilogramme to British troy grains was constructed, to 

 which the value of Mr. Van Svvinden's standard kilogramme 

 has been prefixed. We may perhaps, all at once, lay aside 

 the result deduced from Tillet's operations, as probably the 



* Base du systeme metrique decimal, tome iii., p. 644. 



r f Tillet, Me"m. de 1' Acad. Roy. des Sciences, 1769, p. 384. 



J Dr. Young's Lectures on Natural Philosophy, vol. ii., p. 161. 



Annals of Philosophy, 1821, New Series, vol. ii., p. 154. 



|| Anuuaire du Bureau des Longitudes, 1829, p. 59. 



