Underscore every noun in the following quotation:
The whole history of the earth has been one of gradual development, of
progress, of slow and painful climbing through the ages. Not only have
the hills and the mountains, the rivers and the stars, the trees and
the cattle, the beasts and the birds, been developing; but man
himself--his mind and his body--has been developing. Men are marvelous
little creatures; they have weighed the sun in their balances,
measured the stars and analyzed the light and beauty of the rainbow;
they have sounded the depths of the ocean; they have learned how the
sun and the mountains were born and the rivers were laid in their
mighty beds; they have learned how the seas became salt, what the
stars are made of. They have learned so much, and yet when it comes to
matters of time and space, and law and motion, they still know so
little. The only man who is conscious of his ignorance is he who has
learned a great deal.--_McMillan_.