278 S.W. Holman—Method for Calibrating Thermometers. 
The mean of these results is 30°'4, and this is probably very 
near the true mean annual temperature of the timber line. 
The better the conditions of the determination, the nearer are 
the results to this mean. Mts. Blackmore and Bridger are 
very good cases, being on the border of the Gallatin Valley, in 
which Fort Ellis is situated, and but very few miles distant 
from the latter. Mts. Lincoln and Silverheels are also admira- 
bly situated with respect to Fairplay, but the annual tempera- 
ture of the latter station is not well determined. Pike’s Peak 
Agency are widely separated by many miles of high plateaus, 
which may materially change the conditions of the temperature 
about the mountain. _ 
Should this result, when tested by a wider range of observa- 
tions, hold good, it will afford a very valuable and easily ob- 
tainable isothermal, and also enable one to estimate the height 
of the timber line from thermometric stations at the bases of 
mountain ranges. 
Art. XXIX.—Simple Method for Calibrating Thermometers ; 
by Sinas W. Houtman. 
Tue calibration of a thermometer by most of the methods 
in ordinary use is a tedious and somewhat difficult operation, 
and hence often neglected even in important work. For the 
purpose of supplying a method simple both in observation 
nd computation, and at the same time accurate, the following 
process is described, which, although involving little that 1s 
novel, has not to my knowledge been used before. 
_ First, however, it is necessary to recall to the attention of 
observers the fact that, without calibration correction, the 
b . 
iocremens This practice is much more general than is ordi- 
narily supposed, and has an important bearing upon the accu- 
AC) e work done with such instruments. For the scale 
thus made is merely approximate, the dividing engine or other 
tool being usually changed only at such intervals as to make 
