HYDROGEN. 49 



exposed a sufficient time to the action of the air, 

 even upon the highest mountains. 



Since the oxygen of the atmosphere is continu- 

 ally abstracted from it by various decomposing 

 processes, it would appear that nature must have 

 some mode of renewing a principle so important. 

 Vegetables have been supposed to perform this 

 office, since they always exhale oxygen gas in the 

 day, and particularly when the sun shines. This 

 circumstance may be easily observed by putting 

 some leaves into an inverted tumbler of water 

 placed in the sun-shine. Minute globules of air 

 will be seen rising from the leaves, which, col- 

 lected at the top and examined, will be found to 

 be oxygen. 



HYDROGEN. 



Hydrogen is so called from two Greek words 

 signifying the genei^ator of water, because it is one 

 of the constituent principles of this fluid. It is 

 also one of the ingredients of bitumen, of oils, fat, 

 ardent spirits, ether, and of all the proximate com- 

 ponent parts of animal and vegetable bodies : it 

 forms a constituent part of all animal and vegeta- 

 ble acids : it is one of the elements of ammonia, 

 and of various compound gases. 



It possesses so great an affinity for caloric, that 

 it is impossible to procure it in the concrete or 

 liquid state, independent of combination. Hydro- 

 gen united to caloric forms hydrogen gas. 



Hydrogen gas is the lightest substance whose 

 weight we are able to to estimate; when in its 

 purest state it is about thirteen times lighter than 

 atmospheric air. It is unfit for respiration j ani- 



VOL. II. E 



