502 



Messrs. Garnelley and Haldane. 



Oxygen, 

 per cent. 



Nitrogen, 

 per cent. 



V OlS. 01 



carbonic 

 acid per 

 10,000. 



Marsh-gas 

 and 

 sulphuretted 

 hydrogen. 



Ammonia. 



300 grains of air deprived 

 of water and carbonic acid 

 gave after oxidation. 



Carbonic 

 acid. 



Water. 



19-506 



79 -962 



53 2 



traces. 



" Eather 

 abundant." 



1 •247 grains. 



1"126 grains. 



Unfortunately no information is given as to the condition and means 

 of ventilation of these sewers. 



In 1867 Dr. Miller,* in an investigation on the action of charcoal 

 air filters, made a number of analyses in two London sewers. The first 

 series was made in a clean and well- ventilated sewer, and the second 

 in a sewer described as "tide-locked and ill- ventilated." In the first 

 series (eighteen analyses) he found on an average 10*6 vols., and in 

 the second (six analyses) 80*7 vols, of carbonic acid per 10,000 vols, 

 of air. In neither series could sulphuretted hydrogen be detected, 

 and in both series the ventilation was by means of open gratings. 



In 1877 Beetzf in Munich found 31'4 vols, of carbonic acid, and 

 2*2 vols, of ammonia per 10,000 as an average of five analyses. 



As regards the micro-organisms present in sewer air the only 

 analyses hitherto published are those of Miquel.J He says, "The 

 atmosphere of sewers, always saturated with moisture and constantly 

 in contact with water more or less filthy and loaded with putrefying 

 substances, is heavily charged with bacteria. Judging from a series 

 of experiments made in the sewer of the Rue de Rivoli in the neigh- 

 bourhood of the point at which this sewer joins the large collector of 

 the Boulevard Sevastopol, there are present in the air circulating in 

 this gallery 800 to 900 bacteria per cubic metre "§ (= 0*8 to 0*9 per 

 litre). He also states that the air of the sewer contains an almost 

 constant number of bacteria, and that in summer the air of the Rue 

 de Rivoli may exceed in impurity by five or six times that of the 

 sewer, while in winter the air of the sewer may be five or six times 

 more impure. No details are furnished as to the condition and means 

 of ventilation of the sewer, nor as to the number of analyses on which 

 these conclusions are based. 



* ' Chemical News,' March 13th, 1868. 



f Quoted by Erismann in Pettenkofer and Ziemssen's ' Handbuch der Hygiene,' 

 vol. 2, p. 197. 



X 1 Les Organismes Vivants de 1' Atmosphere,' 1883, p. 273. 



§ These numbers refer to the bacteria capable of developing in a solution of 

 Liebig's extract of 1*024 specific gravity placed in an incubator at 30° — 35°. 



