ORDINARY MEETINGS. XXV 
my endeavor to present a case considerably better than the worst 
which obtains in our school. 
As will be seen, a great variety of conditions is presented. The use 
of the room is intermittent, and when in use, its ventilation depends 
wholly upon the temperature of the outside air. The heating apparatus 
is so inadequate that upon a cold day with all windows closed the 
temperature cannot be brought above 62° F. Hence it is only during 
comparatively warm weather that the windows can be opened at all. 
The laboratory gives an air space of nine cubic meters to each Of 
thirty-four students, due allowance being made for the desks and cases. 
All authorities admit that air containing more than six parts of 
carbon dioxid in ten thousand is injurious, but for various reasons it is 
generally agreed that Pettenkofer’s standard of ten parts of carbon dioxid 
may be used as the outside limit for ordinary school-room air. For 
kindergartens it is thought that the air should never become more 
impure than is indicated by the presence of four parts of carbon dioxid 
in ten thousand. It will be seen that only at the beginning of school 
does the air in the laboratory come within Pettenkofer’s standard. 
From all observations made in all the rooms in the Normal School, 
and in the corridors, the times of making the tests being from 9 a. m, 
to 5 p. m., and the conditions as various as exist in any school building, 
and the dates from March 6 to June Ist. I find the following averages 
for the amount of carbon dioxid in ten thousand parts of air: 
iw aOkOOna, mie ere cas se oe ose PP sin ore : 8.30 
OLA CONE Te RL sr Os 00, ‘Gta GS eee 9.63 
SO SOMC) OS Cs aes orneee NE Peer on Teen 20.33 
Ho TUB) Oe Ca eae eee 2s tabi acca aot eae eee 16.05 
MAO MENTE 2. Hg be Aaa. tools) o 5 Sree mee ae 23.54 
Sys 614d L000 OFes 01 eee a ae aE BO loan Teg 
AS DAO) cht ste, DAS PR ee eR Se Ae Hate OO 
The decrease in impurity from ten to eleven o’clock is due to the 
recess taken by the model school at that time. The great increase after 
3.15 is more difficult to account for, but it seems to me satisfactorily 
explained by these considerations. Ist. During school hours the warm 
air breathed out rises,so that even the heavy carbon dioxid is carried 
upward. When the whole air cools the carbon dioxid is found near the 
floor. 2nd. After school, much blow-pipe work was going on in the 
laboratory, raising the impurity in that room, and the library was usually 
crowded. The average of many five o'clock tests in the latter room gives 
forty-five parts of carbon dioxid in ten thousand of air. 
