1 879 .] Proceedings of Societies. 51 1 
tivity, and considers that the balance is influenced by the density 
as well as by the conductivity of the metal interposed. 
Prof. Hughes said that as the working of metals appeared to 
efleCt their conductivity, he was inclined to rely more on the con- 
ductivity measurements of the balance than on those of the 
Wheatstone bridge. By the balance plain pieces of metal were 
taken, whereas by the bridge wires were mostly taken. He 
would rather not give any theories yet as to the results obtained 
from the balance. 
Dr. Erck then exhibited his novel pump for lifting solutions out 
of batteries. It consists of a closed vessel, funnel-like, the stem 
dipping into mercury, a column of which ascends the latter to a 
certain height. Two tubes emerge from the cover, one dipping 
into the liquid, the other opening to the air. By altering the 
pressure inside the vessel the solution rises to the latter, and can 
escape from it by trickling through the mercury. 
