to ascertain a Standard of Weight and Measure . 135 
thin wire, of which the rod consisted, was too weak to support 
the ball in a state of vibration; and that, after 15 or 20 hours 
action, it repeatedly broke. The same misfortune attended my 
from London. Whether this accident happened from any rust 
in the old wire, or from want of due temper in the new, or 
from its being too much pinched between the cheeks,* I cannot 
tell : I can only observe, that all the wires that I used were con- 
siderably heavier, and therefore probably stronger, than what 
- v • _ 
Mr. Whitehurst mentions, viz. 3 grains in weight for 80 inches 
in length ; nay, mine proceeded as far as from 3 to 6 grains for 
that length, and yet I could never get it to support the ball during 
the whole period of my experiment. This being the case, and 
being in the country, far removed from the manufactory of this 
fine wire, I was reluctantly compelled to relinquish this part of 
the operation to some more favourable opportunity. In the 
mean while, however, I thought it desirable to measure the dif- 
ference of the lengths of Mr. Whitehurst's pendulum from 
his own observations ; for, very fortunately, the marks that he 
had made on the brass vertical ruler of his machine were still 
visible ; and this interval, which he calls “ 59,892 inches,” I 
determined, on my divided scale made by Troughton, from 
Mr. Bird's standard, to be = 59,89358 inches, from a mean of 
four different trials in the temperature of 64°; that mean differ- 
ing from the extremes only = ,0003 inch. 
(§.4.) By this examination, if I have not verified, I have 
at least preserved, Mr. Whitehurst's standard ; and, for the 
present, I shall consider this measure of the difference of the 
length of the two pendulums, vibrating 42 and 84 times in a 
'00&8 y. y 
-0// 4 t 4. 'Oifyjj 
7 
* 0602 $ 
trials with three other different sorts of wires that I had obtained 
* C, C, fig. 1. of Plate II, in Mr. Whitehurst’s pamphlet. 
