on the polygonal reflector, hence the temperature which the solar rays are
capable of imparting to the large heater will be 200.5° × 1.235 =
247.617°; but the energy of the solar rays acting on the _reflector_ is
reduced 0.207 by atmospheric absorption, consequently the ultimate
temperature which the sun's radiant energy is capable of imparting to the
heater is 1.207 × 247.617° = 298.87° F. It is hardly necessary to observe
that this temperature (developed by solar radiation diffused fully
ten-thousandfold) must be regarded as an _actual_ temperature, since a
perfectly transparent atmosphere, and a reflector capable of transmitting
the whole energy of the sun's rays to the heater, would produce the same.

The result of the experimental investigation carried out during the summer
solstice of 1884 may be thus briefly stated. The diffusion of the solar
rays acting on the 20 inch heater being in the ratio of 1 to 10,241, the
temperature of the solar surface cannot be less than 298.87° × 10,241 =
3,060,727° F. This underrated computation must be accepted unless it can
be shown that the temperature produced by radiant heat is not inversely as
the diffusion of the rays. Physicists who question the existence of such
high solar temperature should bear in mind that in consequence of the
great attraction of the solar mass, hydrogen on the sun's surface raised
to a temperature of 4,000° C. will be nearly twice as heavy as hydrogen on
the surface of the earth at ordinary atmospheric temperatures; and that,
owing to the immense depth of the solar atmosphere, its density would be
so enormous at the stated low temperature that the observed rapid
movements within the solar envelope could not possibly take place. It
scarcely needs demonstration to prove that extreme tenuity can alone
account for the extraordinary velocities recorded by observers of solar
phenomena. But _extreme tenuity_ is incompatible with low temperature and
the pressure produced by an atmospheric column probably exceeding 50,000
miles in height subjected to the sun's powerful attraction, diminished