368 . Standards ef univerfal Meafure and ff 'eight, 



be 0,2445589 of the unity. The hollow mark was 0,2445127 ; and tlic folid mark, 

 0,2444675. Whence the differences are: between the mark deduced from the whole pile and 

 a hollow mark 0,87 grains; between the fame and the [folid mark, 1,87 grains; and between 

 the folid mark, and the hollow mark, 0,85 grains. The mark which the celebrated Tillet 

 ufed in his experiments on the weights of different countries, made in 1767, and inferted in - 

 the Memoirs of the Paris Academy for that year *, was different from this pile, though the 

 reporter does not fay what was the difference. 



The flandards prefented to the Inftitute by this commifSon, were the metre in platina, 

 equal at the temperature of melting ice to 443,296 lines of the toife of Peru, this toife being 

 fuppofed to have the temperature 16 and a quarter, as has been already obferved. 



Befides this extraordinary ftandard, other flandards made of iron were alfo prefented for 

 ufe on common occafions. It is recommended that the operations of adjufting meafures 

 of different metals to thefe flandards fhould be performed at or near the 15th degree of the 

 centigrade thermometer, becaufe the fubfequent variations, either to freezing or to a con- 

 fiderable heat, would then produce a lefs difference between the different kinds of metal. 



The ftandards of weight were a kilogramme of platina intended for the legiQative body, and 

 to be preferved with the mofl fcrupulous attention for very important occafions, and feveral 

 other kilogrammes of brafs, made with the fame exacSnefs, and intended for civil ufe. Thefe 

 two kilogrammes of platina and of brafs being truly adjufled, are not equal in air, but only 

 in vacuo. The difference in air is, that the brafs weight is about one grain and two thirds 

 lighter, on account of buoyancy. 



Such are the ftandards which have been produced with great labour, from a courfe of ob- 

 fervations, experiments, and deduftions, capable indeed of being repeated, though not likely to 

 be again performed by a lefs power than that of a public government. What might be the 

 limit of difference between thefe refults and others which might be had by fuch a repetition, 

 can therefore be only eftimated from a fedulous examination of the particulars of this ar- 

 duous enterprize. It will not, however, be neceffary, for the prefervation of the refults 

 of Cit. Mechain and Delambre, to recur to the aftual ftandards which have been here pre- 

 fented ; for, as the reporter points out, it will be fufHcient to render the operation of renewal 

 more eafy if the length of the fimple pendulum at a known place be expreffed in parts of the 

 metre. Cit. Borda, Mechain, and Caffini, have determined this for Paris at the national ob- 

 fervatory, with an apparatus which will be defcribed in a memoir of Borda hereafter to be 

 printed. The length of the fimple pendulum which beats feconds at Paris was found to be 

 0,2549919 of the module fuppofed to be at the temperature of melting ice : whence it is eafy 

 to conclude that this length is 0,993827 of the metre. 



* See alfo the Firft Principles of Chemillry ; and my Chemical Di^ionary, art. Balance. 



r On 



