[B] This term is employed as being most exact and comprehensive, as this fluid is now known to be the source of all life and all attractions.
CHAPTER V.
SUN-HEAT.
Its Source and Limits.
Sun-heat is another product of the same retro-action between the sun and earth; consequently it has the same range and the same boundaries as when it is viewed as light.
Tendencies to unsettle in Science.
The scientists of to-day may well look after the soundness of their favorite theories of the great physical forces; for the uncertain tenure of old theories, by reason of recent discoveries, is becoming but too manifest. New phenomena are now observed which require solutions not met by present hypotheses. The nebular hypothesis which has so long possessed the scientific mind has, by the discovery of the moons of Mars, become a thing of the past. According to M. Maiche, water is found to be no longer the old-fashioned conventional oxygen and hydrogen, but essentially a new element must be considered in estimating its composition.[6] Light is ascertained to be as veritable a substance as water. The sun is recognized to be dark, cool, and habitable. Messages go through the air from kite to kite ten miles apart without visible agency. Telephonic sounds leap from wire to wire through quite ten feet of space.