ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. L L J 
University College, for her paintings; to Mr. Kinnear, Chief of the Sanitary 
Department, for his kindness in constantly furthering our work ; to the Head Masters 
of the various schools we examined, and particularly to the Hectors of the High 
School and Harris Academy. Many other gentlemen have also given us valuable 
assistance, for which we are indebted. The photograph we owe to the kindness of 
Professor Steggall. 
Supplementary Note. 
(Added December, 1886.) 
On dividing the naturally ventilated schools we examined into two classes, accord¬ 
ing as they were heated and ventilated by fires or by hot pipes respectively, we 
obtained the following results. The data for mechanically ventilated schools are 
added for comparison. 
Description of School. 
No. of rooms 
examined. 
Carbonic acid. 
Organic matter. 
Total micro¬ 
organisms. 
Ventilated mechanically, and heated by hot 
20 
12-3 
10-1 
16-5 
air blown into the rooms 
Heated by fires, and ventilated in the ordi¬ 
nary way 
Heated by hot pipes in the room itself, and' 
18 
16-9 
15-7 
169- 
ventilated by windows, ventilators in the 
room, and in some cases by a few Tobin’s 
tubes 
21 
20'0 
16-5 
92- 
The above Table shows that with fires the carbonic acid was considerably and the 
organic matter slightly less than with hot pipes, while the number of micro-organisms 
was very much larger. 
The above average for micro-organisms in schools with fires does, not include the 
four denominational school-rooms. If we include them, the average is 241. The 
number 169 for micro-organisms includes all the Board schools; but those with fires 
have an average age of about fourteen years, whereas those with hot pipes average 
only about seven years. If, however, w T e take only the schools built between 1875 
and 1880, the averages are as follows, and give practically the same results as regards 
the large excess of micro-organisms in schools with fires. 
No. of rooms 
examined. 
Average age. 
Total micro¬ 
organisms. 
years. 
Schools with fires, built 1875-80 . 
7 
2-9 
171- 
„ hot pipes, „ 
13 
35 
108- 
