above or below it, while over more than half the land-surface of the earth the temperature rarely falls below the freezing point.

On the other hand, we have a globe of the same materials and at the same distance from the sun, with a maximum temperature of freezing water, and a minimum not very far from the absolute zero, the monthly mean being probably much below the freezing point of carbonic-acid gas--a difference entirely due to the absence of these three favourable conditions.
_The Special Features of Mars as influencing Temperature._ Coming now to the special feature of Mars and its probable temperature, we find that most writers have arrived at a very different conclusion from that of Mr.Lowell, who himself quotes Mr.Moulton as an authority who 'recently, by the application of Stefan's law,' has found the mean temperature of this planet to be-35 deg.

F.Again, Professor J.H.

Poynting, in his lecture on 'Radiation in the Solar System,' delivered before the British Association at Cambridge in 1904, gave an estimate of the mean temperature of the planets, arrived at from measurements of the sun's emissive power and the application of Stefan's law to the distances of the several planets, and he thus finds the earth to have a mean temperature of 17 deg.

C.( =62-1/2 deg.