"Our birds at that age will lay about twenty eggs, and then proceed to hatch them. For the hatching process they require forty-two days--exactly twice as long as the common hen--and they take turns in sitting on the eggs. There is the same uncertainty with ostriches as with other birds in counting chickens before they are hatched, but we can fairly hope to get ten chickens from twenty eggs. The ostrich raises two broods in a year, so that at the end of the year we have twenty chickens. Next year twenty more, or ten pairs a year from the old birds, and so on, year after year. Then when the chicks are three years old they have broods of their own, and then--" Fred said he must take time to figure up the state of affairs at the end of ten years, and as the supply of paper was limited he wisely paused for the present. Any boy who chooses may make the calculation and easily figure out a fortune for himself and all his partners in the enterprise. Before Fred was through with the calculation he had determined to emigrate to the Cape and become an ostrich farmer; or, better still, he would buy a few thousand acres of land in Arizona, where the country was said to be admirably adapted to this new and highly profitable industry. Doctor Bronson dampened his ardor a little by telling him the ostrich had many enemies, in a domestic as well as in a wild state. "The hyena, wild-cat, and fox," said he, "have a loving tooth for the egg of the ostrich, and will often drive the bird from its nest, so that they may feed on its contents. Crows will drop stones into a nest when the bird is away for a few moments. This was formerly supposed to be a fiction, but its correctness has been verified by several observers. The crow seizes a round pebble from a brook or other place, poises himself over the nest, and then drops the stone with an accuracy that rarely misses its object. He follows to the ground immediately after the stone to make a feast on the broken egg. "Hawks kill the young chicks, and the birds, old and young, suffer from various diseases, most of them caused by improper care." "That is true," said Fred. "My ostrich-eggs shall be hatched artificially. Natural incubation occupies a period of six weeks." [Illustration: WHAT FRED HOPED FOR.] "That's so," chimed in Frank; "the farmers at the Cape use incubators, invented by Mr. Arthur Douglas. Not only do they get more chickens from a given number of eggs, but they get three broods a year instead of two."