Nexv Hypothesis of Earth-Origin. — Fairchild. 97 
ally held in the volatile envelopes. The difficulty in the way 
of harmonizing geological facts with this conception have 
long been recognized by geologists, but have been reserved 
for future solution. 
The new hypothesis claims that the substance of the atmos- 
phere and ocean were originally a part of the planetesimals, 
and helped to form the earth's mass. Whether the elements 
were superficial condensations on the solid planetesimals, like 
the occluded gases of meteorites, or formed part of their es- 
sential substance may not be important to the present discus- 
sion. The really important principle is that these substances 
were world-stuff, and that they were carried into the earth's 
mass by the accreting process of earth-making. A large por- 
tion of the nitrogen, oxygen, hydrogen, carbon, helium, argon 
and other substances, have been subsequently forced from the 
earth's interior to the surface by gravitational condensation and 
the resulting heat. This out-squeezing of the volatile sub- 
stances has been a continJuous process ever since an early 
stage of earth accretion. But the atmosphere did not exist 
until the earth had reached a size somewhat larger than the 
rnoon ; for it appears according to the laws of kinetics and 
judging from the present naked condition of the moon that up 
to that size the gravitational attraction of the earth was not 
competent to hold the gases on its surface. Even to-day the 
molecular velocities of hydrogen and helium seem to be suf- 
ficient to carry the molecules of those gases beyond the earth's 
efficient attraction. The atmosphere and the ocean of to-day 
are only such portions of the gaseous emanations from the 
earth's interior as the earth has been able to hold within its 
grasp, minus the considerable part which has been restored to 
the superficial lithosphere by carbonation and oxydation pro- 
cesses. 
The atmosphere has had a slow growth, from a probable 
film of carbon dioxide to its present volume ; and the growth is 
still in progress through volcanic and other exudations, and by 
release of gases in decay of the jcrystalline rocks. Throughout 
geologic time, as recorded in the stratified rocks, loss and sup- 
ply of the carbon dioxide seem to have been fairly well bal- 
anced, as professor Chamberlin and other writers have shown 
how counterbalancing activities have probably served to check 
