92 
The Americdn Geohxiist. 
Au-ust, 1895. 
thcni. for the first time since observations V)efji;an, during tlie 
last Martian summer of 1894, form an argument so strong as 
to be almost demonstrative in support of this long entertained 
opinion. They bring this planet, our nearest superior neigh- 
bor in the sj^stem, into very close analogy with our own globe. 
It is scarcely relevant to conjure up theoretical objections 
drawn from possible but imaginary dirterences between the 
physical constitution of the earth and Mars. Not the slight- 
est grounds exist for supposing such dilferences. The com- 
munity of material through the universe is so well proved and 
the absence from the other planets of all elements other than 
those with wiiich we are familiar justifies us in assuming iden- 
tity and in believing that the white caps of Mars are composed 
of real snow and ice. 
EXPLANATION OF DIAGRAM. 
Projectiou of tlie orbits of the Earth and Mars ou the plane of the Ecliptic. 
PP. Perihelion point. Eartli lUO" Long. Mars ;««° Long. 
SVE. Southern Vernal Equinox. Mars ;J54° Long. 
SSS. Soutliern Slimmer Solstice. 
SAE. " Autumnal Equinox. 
SWS. " Winti'r Solstice. 
S 1. Eccentricity of orbit of Earth. 
S2. " Mars. 
