280 An Account of the Comparison of 
like truth. The continuous attacks of the exhaustless, though 
weaker, assailant rouse the more gigantic, but intermittent, re+ 
pellent energies of its opponent. It is a war offensive and de- 
fensive. Thus does the contest continue for life with equal suc- 
cess, and at its close remain a drawn battle. 
J. Murray. 
LXV. An Account of the Comparison of various British Stand- 
ards of linear Measure. By Capt. Henry Karer, F.R.S. 
&re* 
Tue Commissioners appointed to consider the subject of Weights 
and Measures, recommended in their First Report “ for the legal 
determinaticn of the standard yard, that which was employed by 
General Roy in the measurement of a Base on Hounslow Heath, 
as a foundation for the Trigonometrical operations that have been 
carried on by the Ordnance throughout the country.” In con- 
sequence of this determination, it became necessary to examine 
' the standard to which the Report alludes, with the intention of 
subsequently deriving from it a scale of feet and inches. 
On referring to the Philosophical Transactions for 1785, it — 
may be seen in “ an Account of the Measurement of a Base on 
Hounslow Heath,”’ that a brass scale, the property of General 
Roy (and now in the possession of Henry Browne, Esq. F.R.S.), 
was taken to the apartments of the Royal Society; and, being 
there, with the assistance of Mr. Ramsden, compared with their 
standard (both having remained together two days previous to 
the comparison), the extent of three feet taken from the Society’s 
standard, and applied to General Roy’s scale, was found to reach 
exactly to 36 inches, at the temperature of 65°. 
It afterwards appears that points, at the distance of 40 inches 
from each other, were laid off on a large plank from General 
Roy’s scale, the whole length being 20 feet; and by means of 
this plank the length of the glass rods was determined, with 
which the base on Hounslow Heath was measured. 
In the Philosophical Transactions for 1795, it is stated, that 
Mr. Ramsden compared Ais brass standard with that belonging 
to the Royal Society, after they had remained together about 
24 hours, when ‘‘ they were found to be precisely of the same 
length.” Brass points were then inserted in the upper surface of 
a cast-iron triangular bar of 21 feet in length, from Mr. Rams- 
den’s standard, at the distance of 40 inches from each other, the 
* From the Transactions of the Royal Society for 182], Part I. 
whole 
