.% 
various British Standards of linear Measure. 337 
If to the above mean ‘000034 be added as before, we have 
-*00273 of an inch, by which the distance from zero to 40 inches 
of Sir George Shuckburgh’s scale is shorter than one sixth part 
of Ramsden’s bar. 
The very great difference between Ramsden’s bar and General 
Roy’s scale, made me desirous of comparing this last with the 
Royal Society’s standard ; and as I was aware of the existence of 
ether standards of considerable importance, I resolved to ex- 
amine them at the same time. 
The Royal Society’s scale has heen described by Sir George 
Shuckburgh : it is of brass, and about the same dimensions as 
General Roy’s scale, which is already well known. It has three 
parallel lines drawn upon it lengthwise. On one of the exterior 
lines marked E, are two dots expressing the length of the Tower 
yard. This is the yard which has been heretofore called, and 
which I shall still call, the Royal Society’s standard. The mid- 
dle line has the Exchequer yard marked upon it; and the other 
exterior line has dots, at precisely the same distance as those of 
the Royal Society’s standard. 
Knowing that Mr. Cary had made for Lieutenant-Colonel 
Lambton a standard scale, which forms the basis of the Trigo- 
nometrical Survey carried on by him in India, and aware of the 
importance of ascertaining the value of this in parts of other 
known standards, I inquired of Mr. Cary whence it was derived, 
and was informed that it had been copied from a scale then in 
the possession of Alexander Aubert, Esq., and which, after his 
death, was purchased by Mr. Jones, of Holborn. On applica- 
tion being made by the Commissioners of Weights and Measures 
to Mr. Jones for the loan of it, their request was readily and 
obligingly complied with. 
This scale is of plate brass, strengthened by an edge bar: it 
contains 6) inches, and has the name of Bird upon it.. Two dots 
upon two gold pins designate the yard, from which the divisions 
of the scale have evidently been derived. There is also a third 
dot, marking, | believe, the length of the French half toise. The 
dots indicating the yard are those I employed. I shall call this 
scale Colonel Lambton’s standard. 
Bird’s Parliamentary standard yard of 1758 had already been 
compared with Sir Geo. Shuckburgh’s seale by him, and recently 
by myself, and found to exceed it about two ten-thousandths of 
aninch. In Sir George Shuckburgh’s ** Account of f experiments 
for determining a standard of weights and measures,” he remarks, 
that there existed another standard yard made by Bird, in the 
year 1760, which did not differ more than two ten-thousandths 
of an inch from the standard of 1758; but he does not say 
Vol. 58, No, 283, Nov. 1821, Uu whether 
