C.—GEOLOGY. 63 
. 3. Approximation to complete adaptation to a given environment is 
' a condition fatal to organisms under adverse circumstances. 
4. Individuals of a species are not necessarily equally adapted. 
5. Replacements rather than transformations is the rule in the 
successive strata of a given locality. 
6. Migration is an important factor in evolution. 
7. Fixation of characters is adverse to evolution. 
8. ‘ Missing links’ are of necessity few in number, widely scattered, 
and disposed obliquely with respect to the strata. 
9. The development of sensibility is only sub-parallel to that of physical 
structure. 
10. The origin of a new race is to be found only in the primitive stock 
of an older race. 
Time and Space—The Age of the Earth. 
The mysteries of time and of space have long been subjects of profound 
contemplation and scientific inquiry ; they are intimately connected with 
the destiny of man and bring him into touch with the infinite. High is 
the cultural value of the mere contemplation of infinity, and of supreme 
importance is any light that may be thrown on a problem long regarded 
as beyond human comprehension. In recent years the theory of relativity 
has opened to the mathematically trained mind a possible avenue to a 
solution, but to most geologists this avenue is a closed road. 
The most majestic of all sciences,. astronomy, has given us, if not a 
solution, at least a better conception of space, and has provided a standard 
of measurement, light years, in terms of which the vast distances of space 
are brought somewhat nearer to our comprehension. Similarly, geology 
has given us a better conception of the vast lapses of time and, together 
_ with physics, has discovered in the radioactive minerals a standard of 
measurement which may eventually prove to be as exact for time as light 
_ years are for space. 
It is well to remember, however, that years do not constitute the only 
standard by which time may be measured, and that, whatever the standard, 
the significance of an occurrence lies in its relationship to preceding and 
succeeding events rather than in the actual number of units of time that 
have intervened between then and now. The geologist gradually acquires 
his point of view, but a degree of maturity in geological thought seems 
to be required before time resolves itself into a succession of events. 
_ The determination of the actual age of the earth has long engaged the 
uttention of philosophers and scientists, and various widely divergent 
estimates have been made by approaching the subject from different 
ntsof view. On the one hand, the earth is a member of the solar system ; 
determination of its age is intimately connected with the history of 
_ that system and falls naturally within the realm of the astronomer and 
the physicist. On the other hand, we have an avenue of approach in the 
succession of events inscribed by the hand of time on the earth’s crust ; 
such investigations fall naturally within the field of the geologist. 
Kelvin, Tait, King, and other great physicists but a few years ago 
lowed the geologist a maximum of 40,000,000 years for the age of the 
earth. Recent studies on radioactive minerals have induced the same 
i school to raise the figure to 1,710,000,000 years, a volte-face that emphasises 
WM 
