Recent Progress in Sanitary Science. 271 



oxj'gen in the earth's atmosphere, and ascertained with accu- 

 racy the amount of the variation in the atmosphere of the same 

 locality and at different points on the earth's surface. The 

 minimum amount for 100 analyses of the air at Paris, was 

 20-913 per cent., and the maximum 20-999, giving as a mean 

 the number 20-956. The lowest percentage in five analyses 

 of the atmosphere of the ocean, was 20-918, the highest 20* 

 965. Of mountain air ; — in that of the summit of Mt. Pichin- 

 cha, which is higher than Mt. Blanc, the oxygen was 20-949 

 and 20-981 per cent. Of all places, Berlin had the distinc- 

 tion of an atmosphere jvith the lowest percentage of oxygen, 

 20-908. This does not appear surprising, when we call to 

 mind the stinking waters of the river Spree flowing through 

 the most crowded portion of the city, under the windows of 

 the Academy of Music, and within a stone's throw of the Em- 

 peror's palace, the Opera-house, the Royal Library, the Mus- 

 eum, and, worst of all, the famous University. To quote the 

 language of Dr. Folsom, the Secretary of the Massachusetts 

 Board of Health — "Berlin and Munich, the filthiest and most 

 scientific of the German cities, deserve Traube's sarcasm of 

 not being able to stop the cholera, even in winter, — a more 

 or less continuous epidemic, so to speak, having lasted since 

 1866 ; while in London and Paris, the cleanest of large cities, 

 the last epidemic (in 1866) fell very lightly, and the death 

 rates are one-third lower than in Munich and Berlin." The 

 mean of all Regnault's analyses was 20-95 per cejit., a num- 

 ber which should be remembered and quoted, instead of 

 twenty-one, the percentage settled upon as a mean, after 

 many experiments, by Gay Lussac and Humboldt, and the 

 one usually given in manuals of chemical science. For it is 

 worthy of note, that the maximum in no one of Regnault's 

 analyses reached twenty-one per cent., while the minimum 

 was never so low as 20-9. 



After Prof. Bunsen had submitted the existing modes of 

 gas-analysis to critical revision, he applied the improved 

 methods to the determination of the oxygen in the atmosphere, 



