stammering and they require the full concentrated power of the
mind. Yet a trained pianist will play a new piece of music at
sight, and perhaps have so much attention to spare that he can talk
with you at the same time. What an enormous number of mental
acquisitions have in this case become almost instinctive or
automatic! It is just so in learning a foreign language, and it
was just the same when in childhood we learned to walk, to talk,
and to write. It is just the same, too, in learning to think about
abstruse subjects. What at first strains the attention to the
utmost, and often wearies us, comes at last to be done without
effort and almost unconsciously. Great minds thus travel over vast
fields of thought with an ease of which they are themselves
unaware. Dr. Nathaniel Bowditch once said that in translating the
"Mecanique Celeste," he had come upon formulas which Laplace
introduced with the word "obviously," where it took nevertheless
many days of hard study to supply the intermediate steps through
which that transcendent mind had passed with one huge leap of
inference. At some time in his youth no doubt Laplace had to think
of these things, just as Rubinstein had once to think how his
fingers should be placed on the keys of the piano; but what was
once the object of conscious attention comes at last to be
well-nigh automatic, while the night of the conscious mind goes on
ever to higher and vaster themes.

Let us now take a long leap from the highest level of human
intelligence to the mental life of a turtle or a codfish. In what
does the mental life of such creatures consist? It consists of a
few simple acts mostly concerned with the securing of food and the
avoiding of danger, and these few simple acts are repeated with
unvarying monotony during the whole lifetime of these creatures.