Regarding the diffusion of the solar rays during the investigation, the
following demonstration will be readily understood. The area of a sphere
whose radius is equal to the earth's distance from the sun in aphelion
being to the sun's area as 218.1² to 1, while the reflecter of the solar
pyrometer intercepts a sunbeam of 3,130 square inches section, it follows
that the reflector will receive the radiant heat developed by 3,130 /
218.1² = 0.0658 square inch of the solar surface. Hence, as the 10-inch
heater presents an area of 331.65 square inches, we establish the fact
that the reflected solar rays, acting on the same, are _diffused_ in the
ratio of 331.65 to 0.0658, or 331.65 / 0.0658 = 5,040 to 1; the diffusion
of the rays acting on the 20-inch heater being as 673.9 to 0.0658, or
673.9 / 0.0658 = 10,241 to 1.

The atmospheric conditions having proved unfavorable during the
investigation, maximum solar temperature was not recorded. Accordingly,
the heaters of the solar pyrometer did not reach maximum temperature, the
highest indication by the thermometer of the small heater being 336.5°,
that of the large one being 200.5° above the surrounding air. No
compensation will, however, be introduced on account of deficient solar
heat, the intention being to base the computation of solar temperature
solely on the result of observations conducted at New York during the
summer solstice of 1884. It will be noticed that the temperature of the
large heater is proportionally higher than that of the small heater, a
fact showing that the latter, owing to its higher temperature, loses more
heat by radiation and convection than the former. 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