Se&. 229. inflammable sub-stances. 445 Oils, bitumens, and charcoal, diftilled dry in a retort, or by their digeftion on the fire ; lime, and even powder of pebbles, digefted in the fame manner with marine acid, or with marine acid air, produce alfo this inflammable fubftance. Its principal properties are as follow: 1 • It is the lighteft of all aeriform fubftances ; viz. 10, or even more times lighter than common air. Mr. Kirwan colle£led it very {lowly over quick-filver; and found it then 12 times lighter than atmof- pheric air. On this account, inflammable air has been employed in the new in vented aeroflates, by the help of which various adventurers have performed aerial voyages with fuccefs. But that inflamma ble vapour, which is formed from vitriolic air, is heavier than common air. 2. It cannot be inflamed without the con currence of atmofpheric air but when mixed with it, in a due proportion, and fet on fire, it explodes with a confiderable noife. If the mixture be of dephlogijiicated air, a detonation is produced as loud, as the report of a piftol [^]; but mixed, or combined ai ns thi$ fluid in itfelf ■ and the experiment of Mr. Kirwan, mentioned above in the text, is a demonftration that there \ s J 10t ne ed of any water or moifture for the produdlion of inflammable air. The Editor. M Inflammable air, on account of its elaftic nature, and of its levity, expands itfelf over a wide fpace, and may have every particle contiguous to 9 fufficient quantity of the dc- phhgifticaui
