EXPERIMENTS ON RADIANT HEAT.

Thames Star, Volume XIV, Issue 4591, 21 September 1883, Page 2

EXPERIMENTS ON RADIANT HEAT.

! ProfessorS. P. Langley, of the A lleg- ! hany Observatory, finds as one of the \ ments that the true solar'constant or amount of heat sent to the earth; is one-; half greater than that determined by Pouillet and by Herschel hear the sea level, -and even greater than the recent valuea assigned by M. Violle; On the other hand, the temperature of space, socalled, is lower than that assigned by Pouillet. If the atmosphere of'the earth were withdrawn the temperature of the latter would greatly fall; even though the sun's radiant heat were materially greater than it is. Mr Langley believes that this temperature under such circumstances would be—sodeg.,F.; that is, that mercury would remain a solid under the vertical rays of a tropical sun if radiation into space were wholly tinchecked, or even if the atmosphere exist- . ing, it let radiations of all wave lengths pass out as easily as they come in. It is not merely by the absorption of the air, ' but by the selective quality of this absorption, that the actual surface temperature of the earth is maintained. Without this comparatively little known function it appears doubtful whether, even though the air supported respiration and oombustionas now, lite could be maintained upon this planet. Accepting these results as true, the temperature of a planet may, and not improbably does, depend far less upon its neighborhood to, or remoteness from, the sun, than upon the constitution of its gaseous envelope, and indeed it i 3 hardly too much to say that we might approxi-* mately indicate already the constitution of ao atmosphere which could make Mercury a colder planet than the Earth, or Neptune aa warm and habitable a one.-* Soientific American.