512 Dr* roebuck’s Experiments , S cc. 
felf examined the beam leifurely and accurately, and 
found it turned very diftindtly with four grains, though 
loaded as above. In order to difcover the caufe of this 
increafe of weight of the cylinder when cold, I heated 
two ounces eight pennyweights of the fcales or calx of 
wrought iron, and found the fame to increafe in weight 
five grains when cold. 
I heated two pieces of pure filver which weighed two 
pounds, ten ounces, five pennyweights ; and when the 
filver was cold it increafed in weight five grains, though 
it produces no calx from being heated red-hot. 
The above experiments are conformable to thofe 
which I formerly made with fome very exact fcales at 
Birmingham ; an account of which I tranfmitted to Dr. 
brockles'by. 
I have the honour to be, See. 
XXXIL Exp* 
