XXXI. Experiments on ignited bodies

Extract of a letter from Dr. Roebuck to Dr. Brocklesby. Mr. Buffon asserts, that he found a ball of iron, which weighed 49 lbs. 9 oz. when cold, to weigh, when heated to a white heat, 49 lbs. 11 oz. which is an augmentation of weight of 19 ⅕ grains to the pound. This extraordinary fact, circumstantially narrated by the very eminent and ingenious M. Buffon, being contrary to the opinions of those philosophers who have most enlarged our natural Knowledge by their candid and cautious inquiry into the qualities of bodies, made me very solicitous to make similar 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 straining 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.