The Archaean hills and mountains, how slowly they melt away!  In the Adirondacks, in northern New England, in the Highlands of the Hudson, they still hold their heads high and have something of the vigor of their prime.

The most enduring rocks are the oldest; and the most perishable are, as a rule, the youngest.  It takes time to season and harden the rocks, as it does men.  Then the earlier rocks seem to have had better stuff in them.  They are nearer the paternal granite; and the primordial seas that mothered them were, no doubt, richer in the various mineral solutions that knitted and compacted the sedimentary deposits.  The Cretaceous formations melt away almost like snow.  I fancy that the ocean now, compared with the earlier condition when it must have been so saturated with mineral elements, is like thrice-skimmed milk.

The geologist is not stinted for time.  He deals with big figures.  It is refreshing to see him dealing out his years so liberally.  Do you want a million or two to account for this or that?  You shall have it for the asking.  He has an enormous balance in the bank of Time, and he draws upon it to suit his purpose.  In human history a thousand years is a long time.  Ten thousand years wipe out human history completely.  Ten thousand more, and we are probably among the rude cave-men or river-drift men.  One hundred thousand, and we are—­where?  Probably among the simian ancestors of man.  A million years, and we are probably in Eocene or Miocene times, among the huge and often grotesque mammals, and our ancestor, a little creature, probably of the marsupial kind, is skulking about and hiding from the great carnivorous beasts that would devour him.

     “Little man, least of all,
     Among the legs of his guardians tall,
     Walked about with puzzled look. 
     Him by the hand dear Nature took,
     Dearest Nature, strong and kind,
     Whispered, ’Darling, never mind! 
     To-morrow they will wear another face,
     The founder thou; these are thy race!’”

I fancy Emerson would be surprised and probably displeased at the use I have made of his lines.  I remember once hearing him say that his teacher in such matters as I am here touching upon was Agassiz, and not Darwin.  Yet did he not write that audacious line about “the worm striving to be man”?  And Nature certainly took his “little man” by the hand and led him forward, and on the morrow the rest of the animal creation “wore another face.”

III

In my geological studies I have had a good deal of trouble with the sedimentary rocks, trying to trace their genealogy and getting them properly fathered and mothered.  I do not think the geologists fully appreciate what a difficult problem the origin of these rocks presents to the lay mind.  They bulk so large, while the mass of original crystalline rocks from which they are supposed to have been derived