66 
State [South Carolina] and have records kept for us near signal-service 
stations in our typical soils—a method which could hardly have been 
arranged with the old form. * * * The great trouble about the 
instrument is the danger in transportation of having the index get 
down in the mercury column. For this reason it has to be transported 
in a box on gimbals to swing freely within a larger box, so that it will 
always remain upright. We had such a box made, capable of carry- 
ing eight or ten instruments. 
From experiments at Houghton Farm (Agr. Sci., Vol. II, p. 50) 
F. E. Emory finds that the thermoelectric couple and galvanometer, as 
used by Becquerel, consumed much time and was frequently useless 
owing to atmospheric electricity and ground currents. Short-stem 
graduated thermometers, with bulbs immersed in oil and fastened at 
the lower end of a light wooden rod, gave good results when the tem- 
perature at the thermometer was not warmer than that of the overly- 
ing soil or the atmosphere; otherwise a circulation of air takes place. 
He finds that the telethermometer, giving a continuous record, answers 
his needs, but we know nothing of its accuracy. 
T. C. Mendenhall (1885) describes a modified form of thermometer 
for observing the temperature of the soil at any depth, which he calls 
the “ differential resistance thermometer.’ Experiments with this in- 
strument at Washington, D. C., have shown him that it is much less 
troublesome than Becquerel’s electric method, but still too trouble- 
some to be recommended to any but persons accustomed to electric 
measurements. Mendenhall’s arrangement consists essentially in util- 
izing the varying resistance of a platinum wire which extends from 
the upper end of an ordinary mercurial thermometer down into its 
bulb. The total resistance diminishes as the temperature rises and 
allows the current to flow through less platinum but more mercury. 
The changes in the resistance are measured by the galvanometer, but 
he hopes to substitute for this the telephone, which will make the 
apparatus more convenient for general use. 
[It is desirable that Mendenhall’s method, or Becquerel’s, or the 
thermophone be provided in connection with the ordinary buried long- 
stem thermometers in order that by an annual or more frequent set of 
comparative observations the changes in the zero point of ordinary 
thermometers may be detected.—C. A. | 
