276 Recent Progress in Sanitary Science. 



Concerning the carbonic anhydride in the atmosphere, but 

 little has been lately added to our scientific knowledge, it 

 being already a well understood subject. But the deter- 

 mination of the amounts of carbonic anhydride present in 

 the air of public buildings — as made in the examination into 

 the defective ventilation of the House of Representatives by 

 the late Dr. Wetherill ; into the air of over-crowded school 

 rooms, as hag been done by the Board of Health of New 

 York ; and that of cars, as in the late investigation of Dr. 

 Nichols of the Massachusetts Institute of Technology; — has 

 been of excellent service in the interests of sanitary science. 

 This is not so much on account of the deleterious nature of 

 carbonic anhydride itself, but for the reason that the ex- 

 halations of the breath are always accompanied by volatile 

 matters and products of organic decomposition, emanations 

 from the body, etc., none of which admit of easy estimation, 

 but whose quantity can be readily inferred from that of the 

 carbonic anhydride. This gas, as we all know, is of a pun- 

 gent agreeable flavor ; and when reference is made to the 

 "closeness" or bad air of rooms, and to the carbonic anhy- 

 dride present, as if the " closeness " and carbonic anhydride 

 were one and the same thing, it is but showing how com- 

 pletely the popular mind has identified the organic pollution 

 of foul air with one, and that not the most unpleasant or 

 most pernicious, concomitant. 



In connection with this subject, it is worthy of note that 

 the eminent sanitary chemist named above, has recently 

 made an examination into the amounts of carbonic anhydride 

 contained in the ground of certain localities below the surface 

 — the ground atmosjjhere. 



The importance of its study, as well as that of the ground- 

 water, was first pointed out by Pettenkofer in 1854, followed 

 in 1870 by systematic determinations of the percentage of 

 oxygen below the surface. The analyses were made upon 

 the alluvial gravel of the country surrounding Munich, in 

 places not under cultivation, with the result of showing, that 



