7 8 PROF. T. CARNELLEY, MR. J. S. HALDANE, AND DR. A. M. ANDERSON 
(e.) One private school [girls). —Three rooms examined. Heated by fires and venti¬ 
lated naturally. 
(f.) The Dundee High School. —Six rooms examined. Ventilated mechanically. 
(g.) The tivo Lecture-rooms and large general laboratory of the Chemical Department, 
University College. —These were frequently examined under various conditions. 
Ventilated mechanically. 
We have thus examined no less than sixty-eight different schools and college class¬ 
rooms, and some of these many times, under different conditions as regards ventilation. 
Of these forty-two were ventilated in the ordinary way by fireplaces, windows, &c. 
(natural ventilation), twenty-six were ventilated by fans which blew air into the 
rooms (mechanical ventilation). 
The comparatively large number of schools in Dundee which are ventilated 
mechanically make it a very good field for testing the relative efficiency of natural and 
mechanical ventilation. The large number of data we have thus been able to obtain 
in schools ventilated on the two systems will, we think, be of considerable interest, not 
only to educationalists, but to all who have to do with the ventilation of public 
buildings. 
The method adopted in all those rooms which are mechanically ventilated'"' is to 
blow air by fans over hot pipes, and thence into the several rooms by broad, shallow, 
upright shafts, opening at a height of five feet from the floor. The vitiated air is 
taken off by shafts which open two feet from the floor and carry the air up into a 
chamber in the roof. Thence it is discharged through louvre-boarded ventilators, 
fitted inside with valves, which prevent any possibility of back draughts. As a rule 
there is an outlet shaft at each end of the room, and one or more inlet shafts on each 
side. The air on entering the room thus passes wholly or partially towards the 
ceiling, and must thence pass downwards to find an exit by the upcast shafts, which 
open near the floor. The current is intended to sweep the whole room in this way, 
while the broad and shallow inlet shafts, through which a large volume of air enters 
at a low velocity, ensure a good distribution of air with as little draught as possible. 
All the schools were examined during the winter months, between December 16, 
1885, and April 28, 1886. They were visited without previous warning, except in one 
or two cases where special experiments were to be made, such as having the ventilating 
fans stopped, &c. We observed the state of the windows before entering; and the 
masters were always good enough to keep them in the same condition during our 
observations as that in which we found them. Hence, if any windows were open on 
our arrival they remained so, or if shut they remained shut, our object being to have 
everything under the usual conditions so far as possible. The samples were collected 
as near the centre of the room as possible. The results are stated in the following 
Table :— 
* For all these Mr. Wm. Cunnixgham, of Dundee, was tlie engineer. 
