gard to the origin and gradual development of the earliest
flint implements will be read with interest; these are similar to the
observations on modern eoliths, and their bearing on the development of
the stone-industry. It is interesting to learn from a letter to Hooker
("Life and Letters", Vol. II. page 161, June 22, 1859.), that Darwin
himself at first doubted whether the stone implements discovered
by Boucher de Perthes were really of the nature of tools. With the
relentless candour as to himself which characterised him, he writes four
years later in a letter to Lyell in regard to this view of Boucher de
Perthes' discoveries: "I know something about his errors, and looked at
his book many years ago, and am ashamed to think that I concluded the
whole was rubbish! Yet he has done for man something like what Agassiz
did for glaciers." (Ibid. Vol. III. page 15, March 17, 1863.)

To return to Darwin's further comparisons between the higher mental
powers of man and animals. He takes much of the force from the argument
that man alone is capable of abstraction and self-consciousness by his
own observations on dogs. One of the main differences between man and
animals, speech, receives detailed treatment. He points out that various
animals (birds, monkeys, dogs) have a large number of different sounds
for different emotions, that, further, man produces in common with
animals a whole series of inarticulate cries combined with gestures, and
that dogs learn to understand whole sentences of human speech. In regard
to human language, Darwin expresses a view contrary to that held by Max
Muller ("Descent of Man", page 132.): "I cannot doubt that language owes
its origin to the imitation and modification of various natural sounds,
the voices of other animals, and man's own instinctive cries, aided by
signs and gestures." The development of actual language presupposes a
higher degree of intelligence than is found in any kind of ape. Darwin
remarks on this point (Ibid. pages 136, 137.): "The fact of the higher
apes not using their vocal organs for speech no doubt depends on their
intelligence not having been sufficiently advanced."

The sense of beauty, too, has been alleged to be peculiar to man. In
refutation of this assertion Darwin points to the decorative colours of
birds, which are used for display. And to the last objection, that man
alone has religion, that he alone has a belief in God, it is answered
"that numerous races have