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estimated on the spot in less than ten minutes, the method used
being simpler and more expeditious than that of Pettenkofer, and
apparently almost as reliable. This apparatus, which bears the name
of the inventor, Dr. Haldane, was provided by the Public Health
Department, and some preliminary experiments have been carried
out by Dr. Sandilands (to whom 1 am indebted for the notes
under this heading), with a view to forming an opinion as to the
reliability of the machine, and to the possibility of its universal use
in any workshop where there might be reason to suppose that
the air was not kept in a reasonably pure state. Owing to a defect
in one of the taps the machine at first gave irregular readings, but
ultimately read accurately in a series of experiments in which it
was checked by Pettenkofer's method and finally by another
Haldane's apparatus.
In 7 underground bakehouses the highest readings were 10 and 11
parts of CO2 in 10,000 of air. These results were obtained in 2 bakehouses
where the ventilation was poor. The experiments wrere
made late on the morning of a warm May day, when all available
means of ventilation were in most cases in use. The air in 7
underground kitchens was sampled, and high readings were
obtained in 2. In 1 of these the excess of CO2 was due to the use
of a gas oven with no hood or other means of preventing the
products of combustion mixing with the air of the kitchen ; in the
other to the presence of two large gas rings and the absence of
sufficient ventilation. Nineteen experiments were made in 12
workshops and factories, and gave the following results: In 4
workshops and 1 factory the air was reasonably pure. In the
remaining 7 it was highly polluted, one room containing no less
than 48 parts of CO2 in 10,000 of air. The high results obtained were
all due to the combustion of large quantities of gas, and the failure
to put in use means of ventilation which were available and would
have been adequate if employed. The highest result obtained from
human respiration alone was 16. If a standard of permissible
impurity, expressed in terms of CO2, were to be established,
Dr. Haldane's machine would be a valuable and convenient means
of enforcing the maintenance of a pure atmosphere, which has