COLLECTIONS OF FACTS. 291 



equilibrium at all times, and in all places. Its elasticity 

 is such, that, however it may be consumed by respiration 

 or combustion, its place is immediately supplied with a new 

 portion, and though, by a mistaken policy, the doors and 

 windows of our habitations may be constructed so as to 

 exclude it as much as possible, it will have admission ; it 

 forces its way through every crevice, and performs the 

 important office assigned it, in defiance of all exertions. — 

 Parke. 



PHILOSOPHICAL FACTS. 



The change of properties which takes place when chem- 

 ical attraction acts, is not confined to metals, but is a gener- 

 al result in every case, where different bodies are brought 

 into this state of combination or chemical union. Fre- 

 quently we find that the properties of each body are totally 

 changed ; and that substances, from being energetic and 

 violent in their nature, become inert and harmless, and vice 

 versa. For instance, that useful and agreeable substance, 

 culinary salt, which is not only harmless, but wholesome, 

 and absolutely necessary to the well-being of man, is com- 

 posed of two formidable ingredients, either of which taken 

 into the stomach proves fatal to life : one of these is a met- 

 al, and the other an air ; the former is called sodium, the 

 latter chlorine. When presented to each other, the vio- 

 lence of their nature is manifested by their immediately 

 bursting out into flame, and instantly they are both deprived 

 of their virulence. Can any thing be more striking than 

 the change of properties in this case ? and who could have 

 supposed that culinary salt is composed of a metal united 

 to an air ? The medicine called Glauber's salts is another 

 instance ; it is composed of two caustic poisons of difTer- 

 ent kinds ; one called oil of vitriol, and the other barilla 

 or soda. There are also two substances known to chem- 

 ists, which are disgustingly bitter liquids ; one is called 

 nitrate of silver, and the other hyposulphate of soda ; when 

 mixed they form a compound of considerable sweetness. 

 But the atmosphere which we breathe is the most extraor- 

 dinary of all instances : it mu<st be surprising to those who 

 are unacquainted with the fact, that atmospheric air, indis- 

 pensable as it is to life, is composed of the same ingredi- 

 ents as that most violent and destructive liquid called aqua 

 fortis, or nitric acid. This powerful acid being made to 



