660 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
bacteria; in a new and fashionable hotel, 360,000; in a well-known 
Fifth Avenue church, 320,000; in the tallest office building in the city, 
850,000; and in the quiet attic of a country house one hundred and 
fifty years old, 110,000 bacteria per gram. 
Dust which had accumulated in the subway contained over twice as 
many molds as dust collected in outside buildings. In the dusts the 
ratio of bacteria to molds was 89 to 1 for the subway, and 250 to 1 
elsewhere. 
ODORS. 
Odors were more or less prevalent at all times and at nearly all 
places in the subway. In some cases they were so faint as hardly to 
be noticeable, in others very decided. 
The effects of the odors upon the passengers varied with the sensi- 
tiveness of the individual. To some persons the odors were exceed- 
ingly offensive, to others they were barely noticeable; many pas- 
sengers soon became used to the odors and did not seriously object to 
them. 
To persons unaccustomed to the subway the odors were unpleasant, 
and suggested that conditions existed which were injurious to health. 
The odors were mest apparent during hot, damp weather, at places 
where the greatest crowding occurred and where the least amount of 
ventilation took place. 
Odors were far more often offensive in the cars than elsewhere, 
especially in the fall and winter months, when the windows were 
closed and the number of passengers was unusually large. 
An effort was made to ascertain the main causes of the odors. It 
was not possible to analyze them chemically or to measure them by 
other means than the senses, although samples of subway dust and 
air, when brought to the laboratory, often smelt unmistakably of the 
subway. By inspections in the subway and repair shops, by examin- 
ing in the laboratory a large number of solid and liquid substances 
taken from the subway, and by attempting to duplicate the odors in 
closed chambers under different conditions of temperature and hu- 
midity, some of the causes of the odors were discovered. 
The following conclusions are, in my view, justified by these 
studies: 
The stone ballast of the roadbed was responsible for part of the 
odor. This stone was made of broken trap rock, and its peculiarly 
slaty odor in the warm atmosphere of the subway was unmistakable. 
It could be most easily distinguished, especially at the more open sta- 
tions, on damp days. 
Frequently the odor of the trap was masked by other odors. 
The oil used in lubricating the wheels and machinery of the cars 
was one of the principal causes of odor. Large quantities of this oil 
