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Page:Popular Science Monthly Volume 18.djvu/375

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361
A JAPANESE TYPHOON.

the fact that his house was at an altitude of two hundred feet above the level of the sea. He declared that the gale was like a typhoon in violence, and that in all the time during which he had lived on the Tay he had never experienced a gale of equal severity. In his opinion the velocity of the wind was from seventy-five to seventy-eight miles per hour, and that during the lulls it would fall to something like thirty.

Charles Clark, who was an amateur observer, gave evidence that 29·00 inches was the minimum point reached; that he had marked the storm 4 on a scale of 6; and that he had never yet recorded 5 or 6.

Other witnesses testified in about the same way, all agreeing reasonably well as to barometric depression and probable velocity.

On comparing these statements with those already made concerning the recent typhoon here in Japan, it will be seen that both in barometric range and in wind-velocity the recent storm considerably exceeded that which was the occasion of the Tay Bridge disaster. The barometric change was not greater, but more sudden in the former than in the latter. Concerning the direct measurement of the pressure of the wind in pounds per square foot, it must be said that the instruments for doing this are, at present, to a great extent crude and unreliable. It is generally assumed that the pressure is proportional to the square of the velocity. Upon a scale adopted by the Smithsonian Institution and by the United States Signal Service, the velocity of twenty-five miles per hour corresponds to a pressure of three pounds per square foot. Assuming the correctness of this, and also of the law given above, the pressure per square foot in the Tay storm must have been nearly thirty pounds, and in the recent typhoon here it must have been nearly fifty pounds. It was shown, in the tests made upon the material of the Tay Bridge, that it might have been expected to give way under a wind-pressure considerably less than forty pounds. The French and many English engineers have adopted fifty-five pounds per square foot as a standard, and about the same number is used in America, but it seems doubtful if even that furnishes a sufficient "factor of safety."

In conclusion, the affirmation may be made, supported as it is by the constantly accumulating evidence of the damage done to buildings, shipping, etc., that this was one of the most violent storms experienced here for many years. From facts already known concerning other points along the coast of Japan, it would seem that, had an efficient system of observations, telegrams, and signals existed, timely warning might have been given of its approach, and possibly much property and many lives saved. In view of this fact it appears hardly necessary to repeat the suggestion, the importance of which has been frequently urged in these columns, that the Government should, at the earliest practicable moment, inaugurate an efficient and complete signal service for the benefit of the whole country.—Japan Weekly Mail.