The New York Rapid-transit Subway

126 CORRESPONDENCE ON NEW YORK SUBWAY. [Minutes of Dr. Soper, dryness was excellent testimony of the thoroughness with which the work of waterproofing had been carried out. Had the subway been wet it would have been excessively uncomfortable in summer. The relative humidity of the subway and streets for about 4 months was given in Fig. 25. The chemical analyses showed that the general air of the subway was by no means deficient in oxygen nor was the carbon dioxide from the lungs of passengers present to an objectionable extent. The highest amount of carbon dioxide found was 8’89 parts per 10,000, the average being 4-81, and the average for the street-air 3-67. The amount of carbon dioxide varied with the place, hour, and season. The method of analysis was Fig. 26. 1905_ PARTS PER 10.000 BY VOLUME Weekly AVERAGE CARBON DIOXIDE IN THE Subway AND STREETS, 10 JULY-25 DECEMBER, 1905. (From 1,772 Determinations.') accurate to within 0 -03 part in 10,000. The CO2 found in the subway and streets over about 6 months was given in Fig. 26. Hourly variations due to differences in the number of passengers carried were shown by Figs. 27. The bacterial analyses showed that there were about half as many bacteria in the air of the subway as in street- air, the average being 3,200 bacteria per cubic metre of air in the