ROCK TEMPERATURES IN VICTORIA. ae 
to conductivity is of the nature for which a correction can 
be applied if necessary. The effect of water upon the tem- 
perature of the walls of the borehole is a rather more trouble 
some factor. There is often a strong current flowing for a 
long time in connection with the drilling operations. This 
happens to be flowing, however, down the centre and up the 
sides, in the way in which it does the least possible harm. 
Circulation of water in the borehole during the experiment 
is the more serious thing to fear, and discs are often used in. 
the rods in order to prevent it. But against this fear must 
be placed the observations made at Wheeling* (U.S.A.), 
where the temperature was taken at the bottom of a deep 
bore 5 inches in diameter. The hole, left without dia- 
phragms for two years, was found to be full of water, but 
its temperature to be within 0°29 Fahr. of what it was 
originally. This, however, is not quite conclusive, as the 
steady state may have been reached before the first experi- 
ment was made, and unfortunately the full paper is not 
‘available here for the detail that would determine the point. 
The deepest reading that we have of underground rock 
temperatures is that of the bore put down by the 
Prussian Government at Paruschurtz, near Rybrick, . 
in Upper Silesia, that reached a depth of 6573-7 feet on 
17th May, 1893. During the next three months a test for 
the temperature was made, and the hole was then started 
again, but was lost a few hours afterwards; 64 stations were 
taken down the hole, with six weight-thermometers at each 
station, and they showed a regular and proportional increase 
of the temperature, from 12° C. at the top to 69° C. at the 
bottom, or a rise in temperature of one degree Centigrade 
in about 115 feet (34:1 metres) of depth. 
There can be no doubt, that all things considered, the 
weight-thermometer, or large elongated bulb of glass, filled 
with mercury, and provided with a capillary overflow, is 
generally the best possible instrument to use for verticle 
boreholes, although it is troublesome, and requires highly 
skilled treatment in order to get the best results. 
The author has not up to the present had any opportunity 
to take the temperatures of deep bores in Victoria, for at 
the present time no suitable ones are in progress; but he 
hopes to do so at the next opportunity. 
Circumstances have, however, been favourable for the de 
termination of the rock-teniperature by the other method, 
* School of Mines Quarterly N.Y., 1897, p. 148. _ 
§ Vereins Mittheilungen zur Oesterreichische Zeitschift fur 
Berg-Lund Hutten Wessen, 1895, p. 108. 
