Besides, the rate of
cooling of heated bodies increases more rapidly than the augmentation of
temperature.
The loss occasioned by the imperfect reflection of the mirrors, as before
stated, is 0.235 of the energy transmitted by the direct solar rays acting
on the polygonal reflector, hence the temperature which the solar rays are
capable of imparting to the large heater will be 200.5 deg. x 1.235 =
247.617 deg.; 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 x 247.617 deg. = 298.87 deg. 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.
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