then

Stem correction = 0.000085 x 200 x (400 - 85) = 5.3 degrees.

As the stem is at a lower temperature than the bulb, the thermometer
will evidently read too low, so that this correction must be added to
the observed reading to find the reading corresponding to total
immersion. The corrected reading will therefore be 405.3 degrees. If
this thermometer is to be corrected in accordance with the calibrated
corrections given above, we note that a further correction of 0.5 must
be applied to the observed reading at this temperature, so that the
correct temperature is 405.3 - 0.5 = 404.8 degrees or 405 degrees.

[Illustration: Fig. 12]

[Illustration: Fig. 13]

Fig. 12 shows how a stem correction can be obtained for the case just
described.

Fig. 13 affords an opportunity for comparing the scale of a thermometer
correct for total immersion with one which will read correctly when
submerged to the 300 degrees mark, the stem being exposed at a mean
temperature of 110 degrees Fahrenheit, a temperature often prevailing
when thermometers are used for measuring temperatures in steam mains.

Absolute Zero--Experiments show that at 32 degrees Fahrenheit a perfect
gas expands 1/491.64 part of its volume if its pressure remains constant
and its temperature is increased one degree. Thus if gas at 32 degrees
Fahrenheit occupies 100 cubic feet and its temperature is increased one
degree, its volume will be increased to 100 + 100/491.64 = 100.203 cubic
feet. For a rise of two degrees the volume would be 100 + (100 x 2) /
491.64 = 100.406 cubic feet. If this rate of expansion per one degree
held good at all temperatures, and experiment shows that it does above
the freezing point, the gas, if its pressure remained the same, would
double its volume, if raised to a temperature of 32 + 491.64 = 523.64
degrees Fahrenheit, while under a diminution of temperature it would
shrink and finally disappear at a temperature of 491.64 - 32 = 459.64
degrees below zero Fahrenheit. While undoubtedly some change in the law
would take place before the lower temperature could be reached, there is
no reason why the law may not be used within the range of temperature
where it is known to hold good. From this explanation it is evident that
under a constant pressure the volume of a gas will vary as the number of
degrees between its temperature and the temperature of -459.64 degrees
Fahrenheit. To simplify the application of the law, a new thermometric
sca