164 JOHN M. SMAIL. 
of earth temperatures conducted for some years past by Mr. 
Russell at the Observatory here, show that nineteen feet below 
the surface the annual range of temperatures has been as little as 
3°8° with a surface shade range of 60:1° and that the maximum 
observed range at that depth seems to have been 5:9°. From this 
it becomes evident that here we have an influence which cannot 
but make itself felt in underground channels, suchas sewers. As 
perhaps making this matter clearer, taking the earth’s temperature 
at Mr. Smail’s quoted level of ten feet below the surface, we find 
from Mr. Russell’s tables for 1889 that in December the mean 
temperature ten feet underground was 64°5° with a range for the 
month of 2°, (the maximum being 65°6) on the surface in the 
shade it was 72:2" mean temperature and a maximum of 99°5° 
with a range of 38°2°. Under such conditions we would naturally 
expect that the air passing into the sewers would be at once cooled 
and of course contracted and rendered denser so gravitating with 
the fall of the drain, and this Mr. Smail’s admirable tests actually 
prove. On the other hand in July of the same year the ten feet 
underground mean temperature was 61°2° with a minimum of 59°8° 
and a range of 2°5°, while on the surface the shade mean was 
_§2°5 with a minimum of 41°6° and a range of 22°8°. These data 
would lead us to expect, what Mr. Smail’s experiments now prove, 
that under these conditions the cold surface air passing into the 
sewers is warmed by the higher earth temperature and so caused 
to rise even against the flow of liquid matter in the sewers. In 
a climate such as ours, when for many purposes coolness is a 
necessity in summer time, such a power as that furnished by the 
natural earth temperature, and one so easily availed of, is surely 
well worth more attention than it has hitherto received. I have 
already urged the importance of this matter in the course of 
public lectures here as far back as 1887, but with the exception 
of a few dairies to which it has been applied this vast store house 
of power is as yet unopened. What is still wanted in the direction 
of rendering this power intelligently available is that a series of 
experiments should be initiated to determine the heat conducting . 
