Notices refpeSling Ne-zv Booh. 2/9 



alwavs . fubje^l to more uncertainty than the latter, Mr. 

 Ward teH us, ih his Mathematics, that he found, by a very 

 nice experiment, that the pound avoirdupoife weighed 6999^ 

 grains trov , and yet we find, from the Report on the Weights 

 of Europe in general, in the Memoirs of the French Academy 

 of Sciences for 1767, that the ratio between the avoirdupoife 

 and troy pounds, which M. Tiliet had obtained for the pur4 

 pofe, was that of 7oo4"5 to 5760. _ '" '' 



" The appreciation of the weight of a cubic inch of di- 

 ftllled water is principally founded on the experiments of 

 Sir George Shuckburgh Evelyn, Bart., defcribed in the Phi- 

 lofophical Tranfd6lion"s for 1798 ; from a mean of which it 

 follows *, that the cubic inch of diftilled water at 60 , under 

 the circumilances defcribed in § 16, weighs 252-506 grains 

 of the Itandard troy pound made for the Committee of the 

 Houfe of Commons in 175H, or 252-8-6 if weighed in va- 

 cuo. 



" A variety of motives concur to induce the authors to 

 take thefe as ilandard experiments. All the older attempts 

 of this kind are of no value whatever, having been made with 

 water which was not di!lilled, and under other circumftances 

 which render them liable to innumerable errors : even the 

 celebrated experiment of Mr. Everard in 1696 was made with 

 undiftilled New River water. The only ones, perhaps, which 

 are at all to be compared with thofe of Sir G. S. Evelyn are 

 thnfe of Dr. Robifon, and the French Comniiflloners of 

 Weights and Mcafures. 



""The former gentleman weighed a cylinder whofe height 

 and diameter were each 6 inches, taken, as he fays, from a 

 mod accurate copy of the Exchc<|uer ftandard, feveral times 

 in diftilled water at 5$'^, and found that it loft 42895 grains 

 of its weight without a variation of 2 grains in the whole. 

 Now, the folld content of the above body being 6' X .785398, 

 or 169-646 cubic inches, a cubic inch of water weiglis in 

 air, according to this experiment, 25285 grains at 55 ; or, 

 by Mr. Gilpin's Tables, exactly 252: at 60'', 



" The authors of this elTay are, however, induced to pre- 

 fer the experiments of Sir G. S. Evelyn to that of Dr. Robi- 

 fon, principally for the following reafon : — lie does not tell 

 us whether his weights had been innnediately and accurately 

 compared with any of the parliameniarv ftandards. The ad- 

 juftnient of the beft weitihts is generally thus performed : — 

 They are, in the firft place, filed to fomething near the re- 

 quired weight; then ground on a ftone, and afterwards po- 



• S.c Pliilofophical journal, O£tavo Scries, vol. iv. p. 35 (No. for 

 Jan. iSoj.) 



T 4 linicd. 



