AIR OF NEW YORK SUBWAY—SOPER. 655 
The average of all results was, for the subway, 4.81 volumes per 
10,000 volumes of air, and for the streets, 3.67; difference, 1.14. This 
difference must be regarded as very slight. (See fig. 4.) 
The frequency with which the air was renewed could not be ac- 
curately calculated, for the reason that the number of passengers 
traveling in the subway was not known. 
At no time or place was the amount of carbon dioxide large. 
The greatest amount of carbon dioxide found in the subway was 
8.89. This occurred in the tunnel between the Grand Central station 
and the Thirty-third Street station, on December 27, 1905, at 6.02 
p.m. At the same time there was a block, during which trains were 
stalled at all points in the vicinity. At the adjoining stations of 
Thirty-third street and Grand Central, the carbon dioxide was higher 
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Fig. 5.—Hourly variations in the amount of carbon dioxide in the air of the subway— 
average of 1,244 analyses. 
than usual at the same time, the amount at Thirty-third street being 
7.84 and at Grand Central 7.87. 
_ The carbon dioxide in the subway varied according to season, hour, 
place where the sample was collected, and other circumstances. 
There was more carbon dioxide found in the autumn than in the 
summer or winter. It seemed likely that this was explainable largely 
on the ground that many more passengers were carried in autumn 
than in summer, and that in winter there was more wind in the 
streets and the subway, increasing the amount of ventilation. 
The amount of carbon dioxide varied in the subway at different 
hours of the day. (See fig. 5.) These irregularities corresponded 
with the irregularities in the amount of travel which took place at 
different hours. 
‘Tt is interesting to note that periodic changes in the amount of 
carbon dioxide occurred in the streets. In the streets the carbon 
