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VENTILATION OF SEWERS AND DRAINS. 163 
Discussion. 
Mr. J. L. Bruce—lI think, sir, it will be mostly admitted that 
the papers which after a]l are of most solid value to the general 
community are those wherein mere theorizing is reduced toa 
minimum, and where practical experimental tests, necessarily of 
course suggested in the first instance by untried theory, form the 
bulk of the communication. Such facts form a firm and immov- 
able foundation for the obvious conclusions which flow from actual 
tests, and so give the data for formule, resting as all formule 
‘should, on good and true “practical work” in the form of carefully 
conducted experimental trials. The paper under discussion is 
emphatically of this class, and that very fact, which renders it all 
the more worthy of careful and thoughtful study, to a large extent 
disarms criticism, or rather rendersitin many directions impossible. 
Experimental facts are of course undeniable, and all that remains 
for discussion is the method in which they have been arrived at, 
and the conclusions drawn from them together with any theoretical 
suggestions for future investigations thereby indicated. 
As my classes at the Technical College prevent my attendance 
at the Society’s meetings, I was deprived of the advantage of 
hearing the paper read, and was dependent for information on 
the print sent to members and which I received only yesterday 
afternoon. I therefore had but scant time to consider the matter, 
but as a few points have occurred to me I venture to lay them 
before the Society, for the most part more as suggestions for 
future investigations than as absolute conclusions. 
First as to sewer temperatures as influenced by earth tempera- 
tures. This is a point to which too little heed has hitherto been 
given, and Mr. Smail has as yet only opened an investigation 
which if continued and widened, will have an immense influence 
on questions of warming, cooling, and ventilation, far outside 
the field of mere drain ventilation. Sufficient has already been 
done by Mr. Smail to show the very direct bearing of this influ- 
ence on the direction and motion of air currents in underground 
channels, The valuable series of observations on this subject 
