"Do you know," said Alec, when he had finished sounding and had reeled up the line, "I once read that the Hudson River can be followed to sea for three hundred miles. That is, there is a distinct furrow or channel in the ocean bottom leading straight from the mouth of the Hudson, as though something had come down that stream and gouged a great ditch in the ocean floor. I reckon it must have been done centuries ago by glacial ice or something of the sort. Anyway, it looks to me as though there is something like that ditch right here in the bottom of the Delaware Bay."
"I wonder what could have made it?" queried Elsa. "Would it make any difference in the oyster-beds along it?"
"By George!" cried Alec, suddenly afire with an idea. "It would make a thundering big slick, that's what it would do, and if my oyster bulletin is correct, that ought to be a prime place for larvæ." He began to examine the water carefully. "That's exactly what it does," he cried, after studying the water far and wide. "We're right in the slick now. It's so big we didn't notice it."
"I guess we were too busy talking to pay attention," suggested Elsa, "or we should have noticed it long ago."
"Well, I can hardly wait to test the water and see what we find," said Alec. "Conditions are just right this morning. The tide has about three feet to rise yet. There ought to be as many oyster fry swimming about now as there ever will be. We'll make as many tests as we can. And we won't strain out so much water as we did the other time. It takes too long. If we test twenty-five quarts of water, that will give us enough to go on. Then we can make more tests."
Quickly Alec had his instruments ready and they began to strain water from the bottom through the bolting-cloth net. Then the sediment was washed into a bottle. While that was settling, they moved on to another spot and strained more water. So they continued until they had several bottles settling.
"Now you begin to count the larvæ," suggested Elsa. "The sediment has all settled in those bottles that we filled first. I will strain out more water while you are using the microscope."
As rapidly as he could, Alec got the sediment on his watch crystals and counted the larvæ. As long as he could hold himself to the trying task Alec continued with his eye to the microscope, picking over the crystalfuls of sediment with his little needles.
"The water's full of them," he cried at last, leaving his microscope. "It's been a mighty poor spawning season, with so much cold weather, though it's warm enough to-day. Yet right here there is no end to the spat. There are ten times as many larvæ here as we found in that ground we tested the other day. Why, that twenty-five quarts yielded 3,400 larvæ," and he picked up the bottle he had just emptied. "The bed's just swarming with spat."
He stepped to the engine and threw on more power. Then he took the tiller. "I want to test a sample from that trough or ditch. And by the way, I'll just sound as we go."