So far as the Signal Service is concerned, the amount of rainfall in the region drained by the Conemaugh river cannot be ascertained. The Signal Service authorities here, to whom the official there reported, received only partial reports last Friday. There had been a succession of rains nearly all of last week. The last rain commenced Thursday evening and was unusually severe.
Mrs. H.M. Ogle, who had been the Signal Service representative in Johnstown for several years and also manager of the Western Union office there, telegraphed at eight o'clock Friday morning that the river marked 14 feet, rising; a rise of 13 feet in twenty-four hours. At eleven o'clock she wired: "River 20 feet and rising, higher than ever before; water in first floor. Have moved to second. River gauges carried away. Rainfall, 2 3-10 inches." At twenty-seven minutes to one P.M., Mrs. Ogle wired: "At this hour north wind; very cloudy; water still rising."
Nothing more was heard from her by the bureau, but at the Western Union office here later in the afternoon she commenced to tell an operator that the dam had broken, that a flood was coming, and before she had finished the conversation a singular click of the instrument announced the breaking of the current. A moment afterward the current of her life was broken forever.
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.
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.