F., he adds: "The sublimation at lower temperatures would be correspondingly increased.

Consequently the amount of water-vapour in the Martian air must on that score be relatively greater than our own." Then follows this remarkable passage: "Carbon-dioxide, because of its greater specific gravity, would also be in relatively greater amount so far as this cause is considered.

For the planet would part, _caeteris paribus_, with its lighter gases the quickest.

Whence as regards both water-vapour and carbon-dioxide we have reason to think them in relatively greater quantity than in our own air at corresponding barometric pressure." I cannot understand this passage except as implying that 'water-vapour and carbon-dioxide' are among the heavier and not among the lighter gases of the atmosphere--those which the planet 'parts with quickest.' But this is just what water-vapour _is_, being a little less than two-thirds the weight of air (0.6225), and one of those which the planet _would_ part with the quickest, and which, according to Dr.Johnstone Stoney, it loses altogether.
* * * * * Note on Professor Lowell's article in the _Philosophical Magazine_; by J.H.Poynting, F.R.S., Professor of Physics in the University of Birmingham.
"I think Professor Lowell's results are erroneous through his neglect of the heat stored in the air by its absorption of radiation both from the sun and from the surface.

The air thus heated radiates to the surface and keeps up the temperature.