PROCESS OF GASSIFICATION. 



they are very seldom, if ever, reproduced, so as 

 to be discoverable by the nicest chemical test. 

 Mr. DALTON, in a place where 200 people had 

 been collected together, for two hours, could 

 only detect one part in 100 of carbonic acid 

 gas, and no hydrogen gas whatever, although 

 a quantity of both gases, must have been 

 given out during that period from the skin, and 

 lungs, of the whole assembly present. 



Dr. PRIESTLEY found thatthe air of places the 

 most offensive and unhealthy, afforded as much 

 pure air, (oxygen) as that of others of an oppo- 

 site description ; the air of crouded cities of 

 low damp situations, or of confined manufacto- 

 ries, was not less pure than the air existing in 

 the most open and champaign country: the nau- 

 seous quality of the air, appearing not so much 

 to depend on any deficiency of oxygen air, as 

 on the presence of effluvia, not discoverable by 

 chemical means ; but which were, nevertheless, 

 made sensible by the sense of suffocation, and 

 oppression, which was felt by the persons pre- 

 sent. Mr. DAVY found, by analysis, that the air 

 from the river Senegal, in Africa, possessed 

 qualities precisely the same as the air of Ham- 

 mersmith, near London. BERTHOLLET ascer- 

 tained, that the air of Egypt, was like the air of 

 France: and Mr. CAVENDISH, likewise, found 

 that the air of various places yielded the same 

 products. DE MARTI, by experiments in 



