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, arid 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 * 

 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 1st. I find the following averages 

 for the amount of carbon dioxid in ten thousand parts of air : 



At 9.00 a. m 8.30 



" 9.40 " 9.63 



"10.00 " 20.33 



" 11.00 " 16.05 



" 1 2.00 m 23.54 



" 3.15 p. m 18.19 



" 5,00 " 29.96 



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. 1st. 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. 



