"Oh, that's all right! And it's only fair, too," said Frank, evidently much relieved.

"S'pose we go out and have a practice this afternoon," suggested Jack. "It's so hot that the water ought to be as warm as milk."

"All right!" said Frank. "Just wait till I leave this parcel at the house and get a couple of towels, and then I'm with you."

Accordingly, a few minutes later the two boys, with towels in hand, were trudging toward the North-west Arm, impatient to be in the water, for the sun was sending down lots of heat that summer afternoon.

Frank Brookfield and Jack Stone were very great friends; had been so, indeed, almost from their nursery days. They got along about as well together as two boys who had each his own share of spirit and selfishness could; and although they were rivals in a good many of their boyish sports, they had a wise way of looking at the matter, for, next to coming out first himself, each was eager that the other should, and consequently they had no occasion to quarrel over the result.

In the science of swimming they were very evenly matched; what Jack lacked in strength as compared with Frank, who stood an inch taller, being about made up by a superiority in style that was natural to him in everything he did.

Hot as the afternoon was, they were too eager for their dip to walk slowly, and when they reached the projecting rock from which they were accustomed to bathe—Black Rock it was called, being a mass of dark, rusty iron-stone—they were both very warm and in a high state of perspiration.

This, however, would not have mattered much if they had undressed immediately and plunged right in; but instead of doing so, they laid aside their outer clothes and then sat down to cool off, thus allowing a reaction to set in that came near having serious consequences.

When they thought they had cooled sufficiently, they finished their undressing and were ready for the water.

"I've half a mind to swim clear across," said Frank, as they stood out on the end of the rock, hesitating for a moment, as all swimmers do, before diving into the cool, green depths.