--Spectroscope gives no evidence of water.


CHAPTER V.

TEMPERATURE OF MARS--MR. LOWELL'S ESTIMATE,
--Problem of terrestrial temperature
--Ice under recent lava
--Tropical oceans ice-cold at bottom
--Earth's surface-heat all from the sun
--Absolute zero of temperature
--Complex problem of planetary temperatures
--Mr. Lowell's investigation of the problem
--Abstract of Mr. Lowell's paper
--Critical remarks on Mr. Lowell's paper.


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