rever.

Sergeant Stewart, in charge of the bureau, says that the fall of water
on the Conemaugh shed at Johnstown up to the time of the flood was
probably 2 5-10 inches. He believes it was much heavier in the
mountains. The country drained by the little Conemaugh and Stony Creek
covers an area of about one hundred square miles. The bureau, figuring
on this basis and 2 5-10 inches of rainfall, finds that 464,640,000
cubic feet of water was precipitated toward Johnstown in its last hours.
This is independent of the great volume of water in the lake, which was
not less than 250,000,000 cubic feet.

Water Enough to Cover the Valley.

It is therefore easily seen that there was ample water to cover the
Conemaugh Valley to the depth of from ten to twenty-five feet. Such a
volume of water was never known to fall in that country in the same
time.

Colonel T.P. Roberts, a leading engineer, estimates that the lake
drained twenty-five square miles, and gives some interesting data on the
probable amount of water it contained. He says:--"The dam, as I
understand, was from hill to hill about one thousand feet long and about
eighty-five feet high at the highest point. The pond covered above
seven hundred acres, at least for the present I will assume that to be
the case. We are told also that there was a waste weir at one end
seventy-five feet wide and ten feet below the comb or top of the dam.
Now we are told that with this weir open and discharging freely to the
utmost of its capacity, nevertheless the pond or lake rose ten inches
per hour until finally it overflowed the top, and, as I understand, the
dam broke by being eaten away at the top.

Calculating the Amount of Water.

"Thus we have the elements for very simple calculation as to the amount
of water precipitated by the flood, provided these premises are
accurate. To raise 700 acres of water to a height of ten feet would
require about 300,000,000 cubic feet of water, and while this was rising
the waste dam would discharge an enormous volume--it would be difficult
to say just how much without a full knowledge of the shape of its side
walls, approaches and outlets--but if the rise required ten hours the
waste river might have discharged perhaps 90,000,000 cubic feet. We
would then have a total of flood-water of 390,000,000 cubic feet. This
would indicate a rainfall of about eight inches over the twenty-five
square miles. As that much does not appear to have fallen at th