204 



Exper'uniHti to a/certain 



Troughton'j weight!. 

 lb. grains. grains. 



The ftandard weight of i troy pound, or J760 grains, marlcedl _ - ,,t 



1758, kept at the houfe of commons, in a fmall box by itfelf, >• ~" ^'^^ > =r 5763,745 

 by Mr. Benfon, weighed - - - - J '74 J 



A duplicate of the preceding, kept with feme other weights, in a"? = i 3,70"? _ , /■„ 

 box marked B - - - ' S fil S ~ ^'^^'^"^^ 



The mean weight of the troy pound, from thefe two 



The two-pounds weight, from the houfe of conimons, kept"? _ 

 in a deal box, marked A - - - 3 ~ 



A duplicate of the laft-mentioned zlb. weight, prcferved in a deal 



box, marked B - - - - 



The thermometer now flood at 68*. 



Therefore the mean weight of alb. troy, from the two laft trials, is 



And confequently ilb. becomes _ _ _ 



But, from the examination of the two fingle pound weights, as above, i pound is 5763,71 



Therefore the mean of all is . - - _ =5763,78 



That is, Mr. Troughton's weights are too light by -jyVoW - = 0,6562 



grain on 1000 grains, or i in 1523,92 grains. 



(§. 42). In conclufion, it appears then that the difference of the length of two pendulums, 

 fuch as Mr. Whitehurft ufed, vibrating 42 and 84 times in a minute of mean time, in the 

 latitude of London, at 1 1 3 feet above die level of the fea, in the temperature of 60", and 

 the barometer at 30 inches, is = 59>89358 inches of the parliamentary ftandard ; from 

 whence all the meafures of fuperficies and capacity are deducible. 



That, agreeably to the fame fcale of inches, a cubic inch of pure diftilled water, when 

 the barometer is 29,74 inches, and thermometer at 66°, weighs 252,422 parliamentary 

 grains; from whence all the other weights may be derived. 



As a fummary of what has been done, I hope it may now be faid, that we have attained 

 thefe three objefts ; 



ift." An invariable, and at all times communicable, meafure of Mr. Bird's fcale of length, 

 now preferved in the houfe of commons ; which is the fame, or agrees within an infenfible 

 quantity, with the ancient ftandards of the realm. 



adly. A ftandard weight of the fame character, with reference to Mr. Harris's troy pound. 



3dly. Befides the quality of their being invariable (without detedion), and at all times 



com- 



