(ilacial Xofeti from the Phutef Mdrs. — ('/(ii/pole. 95 
inches of the mercurial haroiiieter, and at 80' Fahrenheit it 
would equal an inch. One curious etl'ect that must follow is 
the rapid transfer of the vapor from the sunny to the shady- 
side of the planet. The rapid evaporation that must accom- 
pany the high temperature of the Martian summer day must 
produce an aqueous atmosphere of considerable tension which 
must immediately flow otf, more or less completely, to the op- 
posite hemisphere and then condense, probably at once, to the 
solid form. If, as Schiaparelli says, the northern snow-cap 
does not begin to increase until a month after the occurrence 
of the northern vernal equinox, it follows that the shady side 
of the planet cannot be intensely cold or that the quantity of 
water thus transferred is not very great. Both conclusions 
are probably true. Possibly the condensation of the vapor 
near the edge may in part cause the haze there noticed. 
There can be no doubt that of whatever material the as- 
sumed atmosphere may consist it is exceedingly rare in com- 
parison with our own. Mr. Lowell concludes that "in con- 
stitution it does not dilfer greatly from our own and that it is 
heavily charged with water-vapor, but that its density is less 
by a half than that of the air at the summit of the Himalay- 
as." This would equal a mercurial column (on the earth) of 
about three inches. Untler such conditions movement would 
be easy and the transfer of gas or vapor from place to place 
exceedingly rapid. 
From what has been above said it is obvious that no true 
glacial conditions exist on Mars at present. His polar snow- 
caps form regularly eveiy twenty-two months and have done 
so for two centuries past. But they never extend beyond the 
frigid zones of the planet and with the returning sun of sum- 
mer they waste and dwindle, and, as already mentioned, that 
on the south pole has actually disappeared during the just 
ended southern summer. Not so with the earth. Observation 
fails to show any marked reduction of the Antarctic ice-cap 
during our Antarctic summer. It is true that the correspond- 
ing season on Mars is ten months long instead of six. But we 
must bear in mind that the correspoiuling M'inter lasts through 
a whole terrestrial year. It is, however, ])ossible that water 
on Mars is so scarce that no great addition could be made 
to the polar ice-fields by any increase in the length of the 
winter. 
