[ 5°9 ] 
XXXI. Experiments on ignited Bodies. 
By John Roebuck, M. D. F. R. S. 
ExtraEl of a Letter from Dr. roebuck to Dr. 
BROCKLESBY. 
cold, to weigh, when heated to a white heat, 49 lbs. 1 r 
oz. which is an augmentation of weight of 19^ grains to 
the pound. 
This extraordinary fa£l, circumflan dally narrated by 
the very eminent and ingenious M. buffon, being con- 
trary to the opinions of thofe philol'ophers who have moll: 
enlarged our natural Knowledge by their candid and 
cautious inquiry into the qualities of bodies, made me 
very folicitous to make limilar experiments. 
Some time ago, when I was at Birmingham, I had 
very luckily an opportunity, by the aid of two accurate 
balances of my friend Mr. bolton’s; one of which 
would, without draining the beam, weigh a pound and 
turn with one -tenth of a grain; and the other weigh half 
an ounce, and turn with the hundredth part of a grain. 
R. F.‘ 
R. buffon alferts, that he found a ball of 
iron, which weighed 49 lbs. 9 oz. when 
X x x 2 
I heated 
