[ 493 1 
u takes off the effedt of heat and cold as well as 
<c either the gridiron -pendulum (as it is com- 
<c monly called) or the quicklilver pendulum and 
<c this upon fufficient trial for near two years. It has 
tc this advantage of both the fore-mention’d ones, 
“ that it may, by lengthening or fhortening. the 
<c levers, be eaffiy adjufted to the exadt proportion 
u of the difference of the iron and brafs, which nei- 
te ther of thofe kinds is capable of, without very 
<c great trouble and difficulty. I was indeed preju- 
diced again!! the method of doing it by levers, as 
u I had heard the late Mr. Graham fay, that he had 
“ tried levers in different ways, that he found they 
” did not work regularly and freely, but by jerks. 
However, in your method, I am fatisfied, by the. 
<c fulled experience, that they fucceed as well as 
Ci either of the other forts, or perhaps any other kind,' 
(( that may be invented hereafter/' 
Before I conclude this paper, I fhall beg leave 
to acquaint this honourable Society, that, in the 
year 1 748, I made a model of a contrivance to be 
added to a pocket-watch, funded upon the fame 
principles, and intended to anfwer the like pur- 
pofe, as the pendulum above defcribed. And, at 
a meeting of a council of this Society, on February 
15 laft, I produced a watch (which I had made for 
a gentleman) with this contrivance added to it, and 
likewife the model, by which was fhewn to the 
gentlemen then prefent what effedt a final! degree of 
heat would have upon it. But, as I have not yet 
had fufficient trial of this watch, I fhall defer giving 
a particular defcription of this contrivance, till I am. 
