1902-3.] Mr Manley on Electrical Conductivity of Sea- Water. 353 
Preliminary Treatment of Waters. 
On a former occasion when the relative densities of certain 
samples of sea-water were being determined at the temperature 
of 24° C., considerable trouble was experienced owing to the for- 
mation of minute gas-bubbles upon the interior of the walls of the 
pyknometer ; their complete removal was absolutely necessary, but 
this, as a rule, could only be accomplished after much loss of time. 
Other observers have doubtless met with the same difficulty ; but 
I am not aware of any account of the following simple device by 
which it may be entirely avoided. 
A stoppered 500 c.c. flask is thoroughly washed out with portions 
of the water to be examined and 200 c.c. of the water poured in • 
a thermometer is introduced, and the flask is held for short and 
successive intervals at some little distance above a small Bunsen 
flame, the contents being continuously shaken. As soon as the 
temperature of the water has been raised to 26° C. the thermometer 
is withdrawn and the stopper inserted ; the water is then vigorously 
shaken for a time, allowed to stand until free from air-bubbles, 
and is finally poured quietly into some clean and dry vessel, from 
which it can be conveniently drawn direct into the pyknometer. 
By this preliminary treatment we not only ensure with complete 
certainty the entire absence of the vexatious air-bubbles from the 
walls of the pyknometer, but also secure a practically uniform and 
very convenient standard aeration for all samples of water. It is 
almost unnecessary to point out that the presence of air-bubbles 
within the conductivity cell would be equally objectionable, and 
■consequently this process has been employed in all the determina- 
tions with great success. 
Method of determining the Conductivities. 
The condirctivities of the five samples of sea-water were cal- 
culated from the data obtained by the following method. The cell 
was first washed out some three or four times with portions of the 
water to be examined ; the tap was then closed and the cell filled 
up to a certain line near the top. Next, the movable electrode, 
together with the glass tube supporting it, was thoroughly rinsed 
with other portions of the water and immediately placed in its 
