oon found themselves floating in a granite room, with huge
wooden doors closed behind them. The water began to boil around them,
and as it poured into the lock from unseen channels the boat rose
slowly. In a little while the Ethels cried that they could see over the
tops of the walls, and in a few minutes more another pair of big gates
opened in front of them and they glided into another chamber and out
into the river again, this time above the "falls."

"I feel as if I had been through the Panama Canal," declared Ethel Blue.

"That's just the way its huge locks work," said Mrs. Morton. "The next
time your Uncle Roger has a furlough I hope it will be long enough for
us to go down there and see it."

"I wonder," asked Roger, "if there are many more dams like this on the
Monongahela."

"There's one about every ten miles," volunteered the steersman. "Until
the government put them in only small boats could go up the river. Now
good sized ones can go all the way to Wheeling, West Virginia. If you
want to, you can go by boat all the way from Wheeling to the Gulf of
Mexico."

"The Gulf of Mexico," echoed the two Ethels. Then they added, also
together, "So you can!" and Ethel Brown said, "The Indians used to go
from the upper end of Lake Chautauqua to the Gulf in their canoes? When
they got to Fort Duquesne it was easy paddling."

"What is that high wharf with a building on it overhanging the river?"
asked Helen.

"That's a coal tipple," said her grandfather. "Do you see on shore some
low-lying houses and sheds? They are the various machinery plants and
offices of the coal mine and that double row of small houses a quarter
of a mile farther up is where the employes live."

As the boat continued up the river it passed many such tipples. They
were now in the soft coal country, the steersman said, and in due time
they arrived at Millsboro, a little town about ten miles above
Brownsville.

Here Mr. Emerson made immediate inquiries about Stanley Clark, and found
that he had gone on, leaving "Uniontown, Fayette County," as his
forwarding address. "That's the county seat where Hapgood says he copied
his records," said Mr. Emerson. "I hope we shall catch young Clark there
and get that matter straightened out."

As there was no train to Uniontown until the afternoon, Mr. Emerson
engaged a motor car to take them to a large mine whose tipple they had
passed on the way up. The Superintendent was a friend of the driver of
the c