268 
EARTH’S FUTURE 
still left, vast buttes standing alone on the plains which in other 
regions far removed from the Canyon’s rim are themselves deep 
below the surface of the existing ground. 
Where erosion is lacking, it is now possible for the geologist to 
drill deep into the Earth’s crust and thus encounter the various 
strata, exploring now to depths that it would have been impossible 
to reach even a few years ago. In this manner is the history of 
the Earth unfolded. 
What of the other worlds that are now known to be scattered 
in space, sharing with the Earth the status of blocks in the mighty 
edifice of the Universe? Reaching back only to the formative 
stage in its life history when the crust of each world was in pro¬ 
cess of making, we know, at present, only a very few. These are 
the planets which, with the Earth, form the Solar System. Jupi¬ 
ter, the largest, has had, and will have, a prolonged period in 
which to write its own history. In the telescope Jupiter is a 
densely cloud-covered sphere, through which can be dimly seen 
what is suspected as the ruddy glow of its seething and molten 
surface. Owing to its large size and mass it has taken very long 
to cool. Its atmosphere is still composed, not only of the gasses 
known on Earth, but of water-vapor, which will at some time 
condense into seas, and many other substances that are now in a 
solid state upon the Earth. 
The planet which most nearly approaches the Earth in the sim¬ 
ilarity of its surface is Mars. Smaller than the Earth — only 
4200 miles in diameter — its atmosphere is such that one is able to 
see through to the surface below and any change there recorded 
passes under our eyes. It is the province of the planetary astrono¬ 
mer to interpret the changes seen and by long continual observa¬ 
tions not only perfect his knowledge of those data, but also, by con¬ 
sidering the causes which have produced these effects, delve deeper 
into the past history of the planet and that which goes to form it. 
The geological significance of the formations on the planet Mars 
is gone into very fully and in a most interesting manner by Perci- 
val Eowell in “Mars as the Abode of Life.” His chapter on “The 
Genesis of a World,” explains in a delightful way, the terrain 
there seen. 
It appears that, being smaller than the Earth, Mars has never 
had as much water in proportion to its surface — though in pro- 
