REPORT OF ASSISTANT DIRECTOR. 3d 



The last estimation was intended to eliminate errors arising from im- 

 piiriries possibly derived from the long and narrow tube through which 

 the air was collected. Since the out-door air in the afternoon has been 

 found by numerous estimations not to vary materially from the normal 

 average of 4 parts per 10,000, the correction due to the tube becomes 

 1.14, and the corrected results are as follows: 



COs per 10,000 



Lecture hall half au hour before beginning of lecture 7.53 



Lecture hall half an hour after beginning of lecture ILOr? 



Experiment room during lecture : 13. 04 



Meau of outside air 4. 00 



If the hall had been an absolutely closed box, the increase in carbon 

 dioxide due to the presence of 500 persons would have been about 300 

 cubic feet. The quantity observed (supposing the specimen to have 

 been a fair sample of all the air in the hall) was 45 cubic feet, or about 

 one-sixth of the possible increase. 



Specimens were also taken for estimation of organic matter and other 

 contents of the air, but are not to be depended upon as tests because of 

 the leugth and narrow caliber of the collecting tube; since both solids 

 suspended in the air and ammonia tend to adhere to surfaces, and par- 

 ticularly to moist surfaces. 



So far as carbon dioxide can be accepted as an indication of contam- 

 ination in air, these observations do not show an unwholesome condi- 

 tion of the air of the lecture room, but do indicate insufficient ventila- 

 tion. For exact conclusions, specimens should betaken near the floor, 

 near the ceiling, and about ten feet from the floor, at the beginning and 

 end of the lecture, and compared with one another and with the outside 

 air. Larger pipes, of metal, should be used for collection, unless speci- 

 mens can be taken in the hall itself; and estimations of ammonia, both 

 free and " albuminoid," should be made in addition to those of carbon 

 dioxide. 



further examinations of air of lecture room. 



March 6. 

 An average of ten persons present. Outside air damp — melting of 

 a heavy snowfall. 



Carbon dioxide : 

 1 p. m., outside air, 4.6 COi. per 10,000 parts. 

 12.40 p. m., lecture hall, 10.04 CO2. per 10,000 parta. 



