355 
liis vast labours, says : <e I am, indeed, led to hope that my 
readers will adhere to the views which, with many contempo- 
raries, I entertain of the succession of life. For he who looks 
to a beginning, and traces therefrom a rise in the scale of 
being, until the period is reached when man appeared upon 
the earth, must acknowledge in such vforks repeated mani- 
festations of design, and unanswerable proofs of the superin- 
tendence of a Creator.”* This was and is felt to be a point of 
great moment, though we must confess that it is one of those 
points which, to say the least, are very far from being fully 
established. Some modification of Sir Roderick's idea may 
prove true, but not that idea, we think, as it appeared to 
him when he wrote the words we have quoted. Yet enough 
had become certain to convince men that there has been only 
a limited line of life on earth. So far as mineral character and 
the superposition of rocks were concerned, it appears as if 
there may have been an indefinite series of changes going 
on • but what is regarded as the irrresistibly evident pro- 
gress of life, from things of the most humble to beings of the 
most exalted character, seems to shut up the inquirer to a 
belief in the limited character of the creation. 
We have now before us the three great parallel lines along 
which all geological science, properly so called, has been tra- 
velling : the varied mineral character of strata, the varied 
order of their deposition, and the changing character of the 
fossils which they contain. If we trace the progress of the 
science up to the present hour, we find only a development in 
detail of these three great branches of truth, and that develop- 
ment rendering it continually more evident that the present 
state of the earth's surface is the result of a series of material 
changes, as to the nature of which men are yet only beginning 
to see as through a glass very darkly. But from this point, 
I think we pass naturally over into the dreamland of con- 
jectural geology.f 
When we come to consider the speculative divisions of geo- 
logical science, we find ourselves at once in a region where 
men are in conflict equally with all true reason, as with the 
Sacred Scriptures, — a region in which, however, they stand on 
ground of the most un-stable character. It was because of their 
unwise love for pure fancy in the garb of Philosophy, that the 
* Silui'ia, pp. 239, 483. 
t Probably the careful reader will think that we have already passed into 
that region. The succession of life on the earth, which has been thought so 
fully established as a truth in science, is not unlikely to share the fate of some 
other great but too hasty generalizations. 
