freezing point of water--the freezing point being 32 degrees; so that it
requires 1180 times as much heat to raise 1 lb. of water into steam, as to
raise 1180 lbs. of water one degree; or it requires about as much heat to
raise a pound of boiling water into steam, as would raise 5-1/2 lbs. of
water from the freezing to the boiling point; 5-1/2 multiplied by 180 being
990 or 1000 nearly.

136. _Q._--When it is stated that the latent heat of steam is 1000 degrees,
it is only meant that this is a rough approximation to the truth?

_A._--Precisely so. The latent heat, in point of fact, is not uniform at
all temperatures, neither is the total amount of heat the same at all
temperatures. M. Regnault has shown, by a very elaborate series of
experiments on steam, which he has lately concluded, that the total heat in
steam increases somewhat with the pressure, and that the latent heat
diminishes somewhat with the pressure. This will be made obvious by the
following numbers:

Pressure. Temperature. Total Heat. Latent Heat.
15 lbs. 213.1° 1178.9° 965.8°
50 281.0 1199.6 918.6
100 327.8 1213.9 886.1

If, then, steam of 100 lbs. be expanded down to steam of 15 lbs., it will
have 35 degrees of heat over that which is required for the maintenance of
the vaporous state, or, in other words, it will be surcharged with heat.

137. _Q._--What do you understand by specific heat?

_A._--By specific heat, I understand the relative quantities of heat in