Before noon, Alec had made tests in a number of places, working straight out from the shore as he had planned. That gave him a sort of cross-section of the bed, as it were. He decided that he would go over the same ground again at once to see if the flood-tide made any difference in his count. For by this time the tide had almost finished running out.
At dinner time Alec and Elsa headed the Osprey for a little point of land near by. A tree growing back on the point offered shade. They managed to get ashore, though it bothered them to find a place where they could get near to firm ground with the tide so low. Then they fastened the Osprey, and made their way through the rank marsh growths, to the tree. They made a little fire, slung a coffee-pot over the blaze, and toasted some Wieners while the coffee was cooking.
After dinner they went back to the boat and resumed their work, making tests in exactly the same places they had tested in the forenoon. And in the flood-tide they found many more oyster fry than they had in the ebb.
"Looks as though there wasn't much use working on an ebb-tide," said Alec, "though, of course, I might find out after a while what the relative number is in the two tides. But there is a lot I can do in ebb-tide as well as in flood. I can take soundings just as well, and I can examine the bottles even better. I'm going to try to make a sort of topographical map of the bottom. It'll be a poor enough thing, at best, but it will help me to understand about the currents. Then I can examine the currents themselves at flood-tide for larvæ."
Their supper they ate on the Osprey. Then Alec hoisted the sail, and in the gentle breeze that still blew, and with the incoming tide to carry them, they sailed silently and swiftly homeward through the sunset and the gathering dusk. Very different was the river from the stream as Alec had first seen it. Now hardly a boat was visible. They passed only one, The Shark, anchored apparently for the night.
"Elsa," said Alec, as they neared the harbor, "it has been a wonderful day. It has meant everything to me. It will make my whole summer happier. I see clearly enough that this job is going to become mighty tedious. But the remembrance of this day will help me to stick to it, even if I do have to work alone."
"You won't be so much alone as you think," replied Elsa. "You have your wireless, and we can call each other every noon and night. We can talk in the early evening and after Arlington sends out the time and the weather news. If you are going to be out on the water so much, you will want to get the weather forecasts, sure. It makes me nervous to think of you all alone out on the Bay. All sorts of things might happen to you."
"Nonsense," replied Alec. "I'll be as safe and snug as a bug in a rug."
"I hope so. But when I think of you all alone out on that great expanse of water, it makes me shiver. You might be caught in a big storm, or pirates might rob you."
"I thought you had such good judgment," taunted Alec. "Now listen to you."