to ascertain a Standard of Weight and Measure. 167 
Royal Society; and in the Tower. The first alone, indeed, 
bear legal authority, and have been in use for more than 200 
years ; the last is considered as a copy of them, and is not used 
for sizing generally. The two remaining ones are of modern 
date; and, although they do not carry with them at present any 
statuteable authority, yet, from the high reputation and acknow- 
ledged care of the artists who made them, (the celebrated Mr. 
George Graham, and Mr. John Bird,) are undoubtedly en- 
titled to very great respect; and are probably derived from a 
mean result of the comparisons of the old and discordant ones 
in the Exchequer. I shall begin with that of Mr. Graham, 
which contains also the length of the Tower standard laid down 
upon it; will proceed then to Mr. Bird’s, and finally conclude 
with those at the Exchequer. 
(§. 36.) May 5, 1797. I went to the apartments of the Royal 
Society, at Somerset House, and, with the ready assistance of Mr. 
Gilpin, at the kind instance of Sir Joseph Banks, I made the 
following observations on Mr. Graham's* -brass standard yard, 
made in 174,2. This scale is about 42 inches long, and half an 
inch wide, containing three parallel lines engraven thereon, on 
the exterior and ulterior of which are three divisions, expressing 
feet ; with the letter E at the last division, and, by a memoran- 
dum preserved with it in the archives of the Society, is said to 
signify English measure, as taken from the standard in the 
Tower of London. That with the letter F denoting the length 
of the half of the French toise; put on here, by the authority and 
under the inspection of the Royal Academy of Sciences, then 
* This rod was not made by Mr. Graham, bat, at his instance, procured by him 
from Mr. Jonathan Slsson,. a celebrated artist of that time. See Phil. r i rails,. 
Vol. XL II. 
