Meafunment of a Bafe on Hbunflow-Heath. 45 5 
So nice an agreement between two refults, with inftruments 
£0 very different, could not fail to be confidered as aftonifhing ; 
and as it rarely happens, that the graduation of thermometers 
will fo nearly correfpond with each other, as not to occafion a 
much greater error, all were very defirous that it could have 
been farther confirmed by continuing the operation in the fame 
way through a more confiderable proportion of the whole 
length. But befides the tedious nature of the double mea- 
furement, owing to the multiplicity of {lands, platforms, 
coffers, and other articles, that were now fucceffively to be 
moved forward, and for which purpofe it had been found ne- 
ceffary to re-inforce the party of foldiers with fix additional 
men ; the operation had already trained out to a much more 
confiderable length than had been expected ; the fummer was 
now far advanced, and the continuance of good weather un- 
certain; the coffers likewife for the chain, havingbeencon- 
flrudled in a hurry, were found to be defedtive : in Ihort, all 
thefe reafons contributed to induce us to give up, for the pre- 
fent, any farther experiment with the chain, and to proceed 
with the glafs rods alone in the completion of the meafurement. 
Accordingly, on Thurfday the 19th of Augufl, the opera- 
tion with the glafs rods was continued for the five hypothe- 
nufes, from the forty- fourth to the fortieth inclufive. It will 
be remembered, that in proceeding with the deal rods, double 
pickets had been placed in the ground, at the middle of the 
forty-full hypothenufe, or that point which terminated the 
1215th rod, reckoning from the fouth-eaff, or the 1 55th from 
the north-well end of the bafe. Now, in returning to this point 
with the glafs rods, the extremity of the 155th fell Ihort of 
the filk thread llretched from picket to picket, juft one-tenth 
of an inch. The expanfion of the brafs llandard fcale, and 
Vol. LXXV. Ooo 
