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.