The clam of the period, particularly the clam along this reach of the upper Thames, was a marvel in his make-up. He was as large as he was luscious, as abundant as he was both and was a great feature in the food supply of the time. Not merely was he a feature in the food supply, but in a mechanical way, and the first object sought by the boys, after their plan had been agreed upon, was the shell of the great clam. They had no difficulty in securing what they wanted, for strewn all about each cave were the big shells in abundance. Sharp-edged, firm-backed, one of these shells made an admirable little shovel, something with which to cut the turf and throw up the soil, a most useful implement in the hands of the river haunting people. The idea of the youngsters was simply this: Their rendezvous should be at that point in the forest nearest the clump of trees standing solitary in the valley below. They would select the safest hours and then from the high ground make a sudden dash to the tree clump. They would be watchful, of course, and seek to avoid the class of animals for whom boys made admirable luncheon. Once at the clump of trees and safely ensconced among the branches, they could determine wisely upon the next step in their adventure. They were very knowing, these young men, for they had observed their elders. What they wanted to do, what was the end and aim of all this recklessness, was to dig a pit in this rich valley land close to the clump of trees, a pit say some ten feet in length by six feet in breadth and seven or eight feet in depth. That meant a gigantic labor. Gillian, of "The Toilers of the Sea," assigned to himself hardly a greater task. These were boys of the cave kind and must, perforce, conduct themselves originally. As to the details of the plan, well, they were only vague, as yet, but rapidly assuming a form more definite. The first thing essential for the boys was to reach the clump of trees. It was just before noon one day when they swung together on a tree branch sweeping nearly to the ground, and at a point upon the hill directly opposite the clump. This was the time selected for their first dash. They studied every square yard of the long grass of the little valley with anxious eyes. In the distance was feeding a small drove of wild horses and, farther away, close by the river side, upreared occasionally what might be the antlers of the great elk of the period. Between the boys and the clump of trees there was no movement of the grass, nor any sign of life. They could discern no trace of any lurking beast. "Are you afraid?" asked Ab. "Not if we run together." "All right," said Ab; "let's go it with a rush." The slim brown bodies dropped lightly to the ground together, each of the boys clasping one of the clamshells. Side by side they darted down the slope and across through the deep grass until the clump of trees was reached, when, like two young apes, they scrambled into the safety of the branches.