"You must remember," the scientist told them, "that these tiny forms, which look like the most wonderful figures in a fairyland of geometry, exist in such billions that as they die, their light shells fall through the sea like a perpetual rain. Some of them, too, are so very light that it takes them a month to sink to the bottom."
"But what can such tiny bits of things live on, Mr. Collier?" asked Paul; "other animals smaller still?"
"No, my boy," was the reply, "on plants called diatoms. There are over four thousand species of these plants known, which are so small that the microscopic animals readily engulf them. Where it is too cold for surface animal life, as in the Antarctic Ocean, these dead diatoms form the mud on the bottom of the ocean, and in the extremely deep parts, the sea-bed is red clay, but most of it is an 'ooze'—'Globigerina,' as it is called—made up of the shells of those very creatures you have now been seeing on that microscope slide. You drop in and see me at New York, boys," he added kindly, "and I'll show you some models I have made of them."
On arrival at Key West one of the first things that impressed itself upon Colin was the sponge wharf, where tens of thousands of sponges of every sort were drying in the hot September sun. The conversation had run upon sponges very frequently during the voyage, and Mr. Collier, who knew the subject thoroughly from a theoretical point of view, had been of great help to his host. But the economic and commercial side of the question was another matter. From this aspect Colin found that the remembrance of his conversation with Dr. Crafts in Washington stood him in good stead.
"As I understand it, Mr. Murren," he said, as they stood on the wharf together, waiting for an approaching boat, "the government looks on the business of growing sponges much as it does on the growing of wheat or any other form of farming, only it is called aquiculture instead of agriculture. Sponge planting isn't so very different from potato planting."
"It looks entirely different to me," the boy's host replied, as he went down the wharf steps. "I'm sorry Mr. Collier was called away this afternoon, but I may as well give a preliminary look over this sponge-farming business and you
boys might as well come along. There's a man here who wants me to buy his sponge farm. Since Mr. Collier is here I'm not going to decide anything without his advice. He doesn't want you this afternoon, does he?"
Colin hesitated a moment.
"Not as far as I know, Mr. Murren," he answered.