have
been, the chaser could have overtaken her had she kept a straight
course. That was understood.

But the farther they went the more certain it was that this new element
was going to balk them. It was fog. The horizon was masked by it, and
soon the damp feel of it was upon them.

Mr. MacMasters paced the deck anxiously. Not a smudge of smoke did he or
the lookouts raise. But the growing fog cloud would soon have hidden
anything of the kind, even if the oil boat had been near at hand.

"Fog-haunted, Morgan," he said to Whistler, with disappointment. "We'll
run on for a while; but it is hopeless, I guess. You say you know one of
the men aboard that power boat?"

Morgan told him what he knew of the bewhiskered man called Blake; and
also of the little water wheel that was whirling under the waterfall at
the Elmvale Dam, although really, it did not seem to him as though that
little invention could have a serious connection with any alien-enemy
activities.

"I will report the whole thing," Mr. MacMasters said. "But, of course,
the Department receives similar and even less assured testimony every
day, of suspiciously acting persons. The information furnished the
Department has all to be sifted. There may be nothing wrong with this
man Blake."

"If he is working at the munition factory, how comes it that he is out
here on an oil-laden boat?" demanded Whistler, with what he thought was
shrewdness.

"Quite so. You boys are naval apprentices, but you were out fishing
to-day," returned Mr. MacMasters, grimly. "There is an explanation for
everything, my boy."

They ran on for another hour, but more slowly. They did not raise a
craft of any kind, and Mr. MacMasters lost hope.

"I will put you boys ashore at Rivermouth," he said. "You can go home by
rail. I shall not be able to put in at Seacove again to-night. And
Rivermouth is off yonder--within a few miles."

Even in the fog the navigator found the harbor in question without
difficulty. Just as they would have apprehended the presence of a
submarine had one been near. There are very delicate and wonderful
instruments aboard American naval vessels--instruments that may not be
described at present--that enable the officers to apprehend the near
approach of other vessels and their own nearness to the shore as well.

The S. P. 888 made her landfall correctly and slipped into Rivermouth
Harbor like a ghost in the fog. There was a quantity of small shipping
in the place