LVII
CHAPTER X.
HEAT.
B. The Effects of Heat.
291-353.
1. Expansion by Heat.
§ 138. 1) As bodies expand by heat, we may measure tem
perature in examining the regular expansion of a certain body
in consequence of heat. The instrument for measuring temper-
atures is called a Thermometer.For its construction and the
three kinds of mercurial thermometers, see: 291.
§ 139. For changing the degrees of Reaumur’s thermo
meter in such of Celsius or Fahrenheit the following formula
will be found covenient:
n° R = 5/4 n° C = (9/4 n + 32)° F
n° C = 4/5 n° R = (9/5 n + 32)° F
n° F = 4/9 (n - 32)° R = 5/9 (n - 32)° C
The tube must have the same width, every where. Why? Why
should the tube be as narrow as possible? Why the bnlb as small
as possible? Why is the open end sealed by melting the glass?
The space above the mercury must be a vacuum, why?
The thermometer does not show, how much heat is contain
ed in a body.
Remark. The first thermometer was constructed by Drebbel in Holland
(1630); Fahrenheit in Danzig and Reaumur in France added the two
fundamental points with the commencement of the 18th century. The
thermometer of Reaumur is used in Germany, that of Fahrenheit in Eng
land, and that of Celsius in France and in science.
§ 140. Also alcohol may be taken instead of mercury
. Rutherford's maximum and minimum thermometers are
