352 Proceedings of Royal Society of Edinburgh. [sess. 
several instruments were suitably determined with the aid of a 
standard instrument from Kew, and the proper corrections applied. 
Tank for the Conductivity Cell. 
In order to maintain the temperature of the cell and its contents 
constant for any required period, they were surrounded by a large 
zinc tank having a capacity of many gallons, filled with water, and 
furnished with a large ring stirrer. Placed centrally within this 
was a small and cylindrical water-tight chamber, supported upon 
a tripod. The mouth of the chamber was covered with a tightly 
Fig. 2. 
fitting cork bung, which had been heated for some time in molten 
paraffin wax, so as to render its insulating properties as, effective as 
possible ; suitable holes had previously been made in the bung for the 
reception of the conductivity cell, the wire leading to the, lower and 
fixed electrode and a thermometer. Pig. 2 shews the cell charged 
and placed in position, ready for a conductivity determination. 
It was found that the contents of the cell usually attained the 
temperature of the tank water in about an hour, but in no case 
were any final measurements of an electric conductivity made 
until after three, and in some cases four, hours had expired. 
