182 DR. R. A. SMITH ON AIR FROM OFF THE MID-ATLANTIC, 



The air from off the Atlantic is seen to contain more 

 oxygen than any of the others. I did not expect that with 

 such a small number any average could be obtained that 

 could be usefully compared with other results ; but we find 

 here that the amount of oxygen is almost identical with 

 that found by me in the air on the sea-shore and open 

 heaths of Scotland^ and the amounts found by others in 

 places where the best air was obtained. In other words, 

 this air stands in the first class as regards oxygen^ and 

 we could expect nothing less. 



The amount of carbonic acid could not be taken with 

 confidence in the small quantity of air at command. 



Perhaps in making these experiments we ought to be 

 more careful in following the movements of nitrogen also. 

 We are apt to allow that this gas makes way for the others, 

 and undergoes no change itself. Of the three important 

 gases of the air, this is the least liable to change. If the 

 nitrogen remains constant, or nearly so, and the oxygen 

 varies as much as I believe proved, is it only to make 

 room for the constant quantity of 200, 300, or 400 of car- 

 bonic acid in a million, as always found ? By more careful 

 observation we should add to our ability to say if the oxygen 

 is found in the same condition as oxygen gas usually is, or 

 if it is condensed, either by being combined- or changed 

 allotropically ; we are in fact groping about for some 

 powerful oxidizing agent which most persons allow to exist 

 in the air in varying amounts more powerful than ordinary 

 oxygen, although acting as oxygen. We are much in the 

 condition of Hooke and Mayow when looking for oxygen, 

 they found what they called a nitro- aerial principle in the 

 air ; in other words, that which is the characteristic of nitre. 

 The question whether the powerful agent alluded to is ozone 

 or some other thing is a minor one, although of the greatest 

 interest. Although the amount is small, we can perceive 

 it in breathing with the greatest ease ; the effect is pro- 



