141 



Air is sometimes deprived of its elasticity, and wrought 

 into the substance of other bodies, from which never- 

 theless it may be extracted, and resume its elastic state. 

 As to animal substances, a very considerable quantity of 

 air is extracted from them by distillation, not only from 

 the blood and fat, but also from the most solid parts of 

 animals. Haifa cubic inch of a fallow deer's horn pro- 

 duced 117 cubic inches of air; half a cubic inch of 

 oyster shells no less than l6'2 cubic inches. 



As to vegetable substances, half a cubic inch of heart 

 of oak generated 108 cubic inches : a cubic inch of peas 

 3$)6 cubic inches, or 113 grains, which was above a third 

 of its weight. This air will flash if touched with a 

 caudle. 



Camphire generates no air: brandy next to none:, 

 well-water, or rain-water, a little pynnont-water, twice 

 as much : which air contributes to the briskness of this 

 and other mineral waters. 



From minerals much air may be extracted. Half an 

 irtch of Newcastle coal yielded 1 80 inches of air, which 

 weighed near one third of the coal. 



Yet a good part of the air extracted from these 

 bodies in some days gradually lost its elasticity, because 

 the acid, sulphureous fumes, raised with the air, re- 

 sorbed and fixed the elastic particles* But when a 

 means was found to prevent this, it lost only a seven- 

 teenth or eighteenth part ; and that chiefly in the first 

 twenty-four hours ; the rest was permanently elastic. 



There is another way of producing air, which seems 

 to be jnore natural, namely, by fermentation^ A cubic 

 inch of * oil of vitriol, with half an inch of sal ammoniac 

 generated six cubic inches of air ; six inches of powdered 

 oyster-shells, and an equal quantity of white-wine vinegar, 

 generated twenty nine inches. 



* Mr. Gsqffry shews that the mixture of any vitriolic salfs with 

 iuflammuble substances will yield common brimstone; particu- 

 larly or' oil of vitriol with oil of turpentine. Brimstone there- 

 fore is nothing but vitriolic salt united with some combustible 



