70 
MR. H. TOMLINSON ON THE INFLUENCE OF STRESS 
The Alteration of Electrical Conductivity produced by Stress applied 
EQUALLY IN ALL DIRECTIONS. 
Unsuccessful attempts and mode of determining the lowering of the melting- 
point temperature of ice. 
So far back as the winter of 1877 I attempted to detect and measure the effect on 
the electrical conductivity of wires produced by such alterations of fluid pressure as 
could be obtained by means of the air-pump only, being under the impression at that 
time that the change of conductivity caused by rise of temperature was due for the 
most part to mere expansion. 
In the first attempt the wire to be tested, a silk-covered copper wire about 12 feet 
in length and ^jth of an inch in diameter, after having been well soaked in melted 
paraffin wax was coiled in a spiral and placed in a thin, hollow, brass tube (fig. 13), 
having an inner diameter of 2’8 centims. and a length of 15 centims. 
Fig. 13. 
The ends of the wire were soldered to two stout copper wires A A, which passed 
air-tight through an indiarubber cork and served to connect the wire under examina¬ 
tion with the comparison-wire. The latter having its ends soldered to the two stout 
copper wires B B, was wound double round the outside of the hollow cylinder, and 
was, together with B and B, secured to the cylinder by string ; the comparison-wire had 
also been soaked in melted paraffin wax, and the four stout wires, A, A, B, B, and their 
junctions with the other wires, well coated with shellac varnish. The two wires, which 
as usual were of the same dimensions and substance, were joined up with the other 
parts of the bridge in the manner already described, and the tube C served to connect 
