Lake and River Temperatures. ig) 
or three feet of ice, have in early August a general temper- 
ture of 76° to 77°: that the air in direct contact with the 
warm surface of the water has, in that month, its tempor- 
ature raised to from 1° to 5° above that of the air directly 
above but in more exposed positions: and that this increase 
of temperature, which is greatest at the point of contact, 
is, at one foot above the surface of the water, already to a 
considerable extent lost. 
ON THE COLLECTION OF SAMPLES OF WATER FOR 
BACTERIOLOGICAL ANALYSIS. 
By Wyarr Jounston, M.D., Montreal. 
IT have been prompted to describe my method of collect- 
ing samples of water for bacteriological examination, in the 
hope of its being of service to those who are anxious to do 
field work in this department of bacteriology. 
Certain principles govern this work which cannot be neg- 
lected without introducing serious sources of error. First, 
the bottles in which the samples are to be taken must be 
sterilized by a dry heat of 150° C. and afterwards kept out 
of the reach of contamination from outside sources (espe- 
cially from dust) until the moment when the water is col- 
lected. To this end the mouths of the bottles must be kept 
from contact with the fingers, and the stopper is only to be 
removed in the water. Second, the manipulations must be 
rapid enough to permit of a large number of separate 
gamples being collected, and finally, these should be taken 
from such points as will ensure their affording a fair index 
of the body of water under examination, as the number of 
bacteria in samples taken at different places from the same 
water often varies considerably. 
The method usually adopted, that of immersing the bottle 
at arm’s length and removing the stopper under water, 
though fraught with much personal discomfort in cold 
weather, is tolerably secure from contamination at the 
mouth of the bottle, but it has the disadvantage ofonly giving 
