CHAPTER VI.
A NEW ESTIMATE OF THE TEMPERATURE OF MARS, --Langley's determination of lunar heat --Rapid loss of heat by radiation on the earth --Rapid loss of heat on moon during eclipse --Sir George Darwin's theory of the moon's origin --Very's researches on the moon's temperature --Application of these results to the case of Mars --Cause of great difference of temperatures of earth and moon --Special features of Mars influencing its temperature --Further criticism of Mr. Lowell's article --Very low temperature of arctic regions on Mars.