s have broken into voice.
Agassiz's zoology causes each youth to be a veritable Noah, to whom it
is given to behold all insects and beasts and birds going two by two
into the world's great ark. God hath given us four inferior teachers,
including travel, occupation, industry, conversation, and four
teachers superior, including love, grief, death--but chiefly books.

Wisdom and knowledge are derived from sources many and various. Like
ancient Thebes, the soul is a city having gates on every side. There
is the eye gate, and through it pass friends, a multitude of
strangers, the forests, the fields, the marching clouds. There is the
ear gate, and therein go trooping all sweet songs, all conversation
and eloquence, all laughter with Niobe's woe and grief. There is
conversation, and thereby we cross the threshold of another's mind,
and wander through the halls of memory and the chambers of
imagination. But these faculties are limited. The ear was made for one
sweet song, not for a thousand. Conversation is with one friend
living, not with Pliny and Pericles. The vision stays upon yonder
horizon; but beyond the line where earth and sky do meet are distant
lands and historic scenes; beyond are battle-fields all stained with
blood; beyond are the Parthenon and the pyramids. So books come in to
increase the power of vision. Books cause the arctics and the tropics,
the mountains and hills, all the generations with their woes and wars,
their achievements for liberty and religion, to pass before the mind
for instruction and delight. And when books have made men
contemporaneous with Socrates and Cicero, with Emerson and Lowell,
when they have made man a citizen of every clime and country, they go
on to add advantages still more signal. When the royal messenger
brought Newton the announcement of the honor bestowed upon him by the
Queen, the astronomer was so busy with his studies relating to the
"Principia" that he begrudged his visitor even an hour of his time.

The great man was too busy writing for thousands to talk long with a
single individual about his discoveries of light and color and his
proofs of the moon ever falling toward the earth. Not even to his best
friends could the astronomer unfold through conversation what he gives
us in his "Principia." When an American author called upon Carlyle he
found him in a very peevish mood. Through two hours he listened to
this student of heroes and heroism pour forth a savage tirade ag