30O Experiments to a/certain 



It is obvious, that by adding a hook to the perforation at the extremity of the divided arc, 

 and a ring in the eye of the ftopper,this inftrument may be ufed for weighing : the divifions 

 are half kilogrammes; (they might conveniently be pounds avoirdupois). 



IV. 



^n Jccount of fame Endeavours to afcertain a Standard of Weight and Meafurt. By Sir 

 George Shuckburgh EvELYNt Bart. F.R.S. and A.S. Continued from p. 157. 



VS' iS-l J^ HE chief ftandards of longitudinal meafure, as far as I can learn, that carry 

 any authority with them, are thofe preferved in the exchequer ; in the houfe of cemmons ; at 

 the Royal Society, and in the Tower. The firft alone, indeed, bear legal authority, and 

 have been in ufe for more than 200 years ; the lall: is confidered as a copy of them, and is 

 not ufed for fizing generally. The two remaining ones are of modern date ; and, although 

 they do not carry with them at prefent any ftatuteable authority, yet, from the high reputa- 

 tion and acknowledged care of the artifts who made them (the celebrated Mr. George 

 Graham, and Mr. John Bird), are undoubtedly entitled to very great refpedt ; and are pro- 

 bably derived from a mean refult of the comparifons of the old and difcordant ones in the 

 exchequer. I fliall begin with that of Mr. Graham, which contains alfo the length of the 

 Tower ftandard laid down upon it; will proceed then to Mr. Bird's, and finally conclude 

 with thofe at the exchequer. 



(§. 36.) May 5, 1797. I went to the apartments of the Royal Society, at Somerfet 

 Houfe, and, with the ready afliftance of Mr. Gilpin, at the kind inftance of fir Jofeph 

 Banks, 1 made the following obfervations on Mr. Graham's * brafs ftandard yard, made in 

 1742. This fcale is about 42 inches long, and half an inch wide, containing three parallel 

 lines enirraven thereon, on the exterior and ulterior of which are three divifions, exprefling 

 feet, with the letter E at the laft divifion ; and, by a memorandum preferved with it in the 

 archives of the fociety, is faid to fignify Englifti meafure, as taken from the ftandard in the 

 Tower of London. That with the letter F denoting the length of the half of the French 

 toife, put on here, by the authority and under the infpedion of the Royal Academy of 

 Sciences, then fubfifting at Paris, to whom it was fent in 1742, for the purpofe of comparing 

 the French and Englilh meafures. The middle line, marked Exch. of the three abovemen- 

 tioned, denotes, as is fuppofed, the ftandard yard from the exchequer. 



(§• 37') '^^'* ^^^ °^ ^''* Graham's had been previoufly laid together with my fcale divided 

 by Mr. Troughton, for twenty-four hours, to acquire the (ame temperature; they were alfo 

 of the fame metal, and, by placing it under my microfcopes, adjufted to the interval between 

 10 and 46 inches, I found the interval on the Tower ftandard exceed 



* This rod was not made by Mr.*Graham, but, at his inftance, procured by him from Mr. Jonathan Siflbn, 



a ctlebrstcd anift of that time. See Phil. Tranf. Vol. XLII. 



mine, 



