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instrument in scientific hands, by which important work may 
be done in the course, perhaps, of centuries. 
There were now, however, three great general ideas esta- 
blished in scientific minds. Certain rocks, deep in the earth's 
crust, or high on the sides of lofty mountains, were seen to have 
been formed in the same manner as similar rocks are now in 
the course of formation in the bed of the sea. The masses of 
sandstone that lie buried so many fathoms down, or have been 
raised so many thousands of feet high, were once sand-beds 
washed by the waves that now wash the sandbanks over 
which they flow. It was not yet within reach to tell how the 
rocks were formed on which the sand was first laid down ; and 
it is not yet, we think, within reach of science to tell this 
secret. The limestone could be traced to its formation by the 
living creatures, and otherwise from the ocean, and it could be 
seen in course of deposition on that ocean's bed. How the 
first bed was formed in which the shell-fish lived, or on which 
the ooze was first thrown down itself, was and is the grand 
mystery. But the discovery of the truth, that deeply hid 
masses had been formed at one time on the surface, and that 
masses now high up the mountains, had been formed in the 
depths of the ocean, was the opening of a vast field of thought 
for men. Then there was the order of superposition, teaching 
that difference in age is irresistibly evident from difference of 
place in that order. That which is now forming on the surface, 
must, as to its formation, be new; that over which it is 
forming, must, as to its formation, be older. Strata laid con- 
formably on each other, show that they were formed during 
one series of changes, while those on whose edges they have 
been laid down, have been formed during a very different 
series ; and so on, as far as men can make out the actual facts 
of the order of deposition. But the grandest of all the teach- 
ings of these discoveries, was found in the order which seemed 
to be disclosed by the fossil contents of the strata. Man was 
on the surface, but no trace of his existence could be found, 
except on that surface. Creatures approaching man in his 
material structure, were found in the relics of their existence 
some way down, but only a short way ; and just as the search 
descended, the class of being discovered was “low " in the 
scale of life. Not that it was less perfect in its kind. As Sir 
Roderick Murchison says : “ When first created, the Onchus 
of the uppermost Silurian rocks was a fish of the highest and 
most composite order ; and it exhibits no symptoms whatever 
of transition from a lower to a higher grade of the lamily." 
Only it was a fish and not a -reptile. This truly eminent geo- 
logist, speaking of one of the great objects he had in view in 
