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Show Nlrsns Hnow on tun. H Prof, Johnstone Stoncy, In develop- H Ing his theory of the csrapo of gases ' H from planetary atmospheres depending M upon tho force of gravity of the par M tlcular planets concerned, has conclud- M ed that helium at present Is slowly es- IH caplng from the earth, and In n distant H past tlmo It probably escaped much M moro rapidly Prom Mara, he says, H water vapor must havo escaped with H about tho snmo readiness as helium H fled from tho earth, nud accordingly H tho variable white patches about tho H poles of Mars are not snow, but proba- H lily arn frozon carbon dioxide. Other H npppearnnrca frequently observed on H Mars are due, he thinks, to low-lying H fogs of carbon dloxldo vapor shifting H alternately between the poles and tho H equatorial regions. H |