THc; EARTH. 0J5 



tni!C<?, made liy the alteration which the minenil or phint has 

 uiiiJergone by the texture of" its parts being loosened in the 

 operation — having shown, I say, that this air may be drawn in 

 gi-eat quantities from vegetable, animal, or mineral substances, 

 such as apples, cherries, amber burned, or hartshorn^ — he in- 

 cluded a frog in artificial air, produced from paste ; in seven 

 minutes space it suffered convulsions, and at last lay still, 

 and being taken out, recovered no motion at all, but was dead. 

 A bird inclosed in artificial air, from raisins, died in a quarter of 

 a minute, and never stirred more. A snail was put into tlie re- 

 ceived, with air of paste ; in four minutes it ceased to move, and 

 was dead, although it had survived in vacuo for several hours : so 

 that factitious air proved a greater enemy to animals than even a 

 vacuum itself. 



Air also may be impregnated with fumes that are instantly 

 fatal to animals. The fumes of hot iron, copper, or any other 

 neated metal, blown into the place where an animal is confined, 

 instantly dostroy it. We have already mentioned the vapours in 

 the grotto Del Cane suffocating a dog. The ancients even sup- 

 posed, that these animals, as they always ran with their noses to 

 the ground, were the first that felt any infection. In short, it 

 should seem that the predominance of any one vapour, from any 

 body, how wholesome soever in itself, becomes infectious ; and 

 that we owe the salubrity of the air to the variety of its mix- 

 ture. 



But there is no animal whose frame is more sensibly affected 

 by the changes of the air tlian man. It is true, he can endure a 

 greater variety of climates than the lower orders generally are 

 able to do ; but it is rather by the means which he has discover- 

 ed of obviating their effects, than by the apparent strength of his 

 constitution. Most other animals can bear cold or hunger bet- 

 ter, endure greater fatigues in proportion, and are satisfied with 

 shorter repose. The variations of the climate, therefore, would 

 j.iobably affect them the less, if they had the same means ot 

 fikill in providing against the severities of the change. How- 

 ever this be, the body of man is an instrument much more 

 nicely sensible of the variations of the air, than any of those 

 which his own art has produced ; for his frame alone seems to 



? Rnvl,-'- Phy^icii-Mi'i'han. vdl. ii. p 3as 



