. Electric railway journal . appealed to usalso. The apparatus can be made of materials availablearound any power plant at very slight expense. After some experiments to determine the best weight TYPICAL SEISMOGRAPH CURVES SHOWING DIFFERENT INTEN-SITIES OF VIBRATION. SCALE APPROXIMATELYONE-HALF SIZE of bob, and finding that one of 60-lb. weight was un-steady, we settled on about 120 lb. as the minimumweight which should be used. The construction of thehome-made seismograph is as follows: The apparatus consists of a tripod about 8 ft. highmade of 2-in. x 4-in. lumber hinged at the top to atrian
. Electric railway journal . appealed to usalso. The apparatus can be made of materials availablearound any power plant at very slight expense. After some experiments to determine the best weight TYPICAL SEISMOGRAPH CURVES SHOWING DIFFERENT INTEN-SITIES OF VIBRATION. SCALE APPROXIMATELYONE-HALF SIZE of bob, and finding that one of 60-lb. weight was un-steady, we settled on about 120 lb. as the minimumweight which should be used. The construction of thehome-made seismograph is as follows: The apparatus consists of a tripod about 8 ft. highmade of 2-in. x 4-in. lumber hinged at the top to atriangular block. Suspended from this block on a pieceof piano wire is a 117-lb. weight. At the bottom of theweight is attached a piece of gage-glass tubing in whicha stylus of small-diameter tool steel is fitted. Thisstylus is so accurately fitted that with a lubricatingfilm of oil between it and the glass tubing there is nolateral play. The vertical motion, however, is perfectlyfree. A trough is placed underneath the weight and. GENERAL VIEW OF SEISMOGRAPH ON POWER HOUSE ROOF AND NEAR VIEW SHOWING VIBRATION RECORD BEING TRACED ON SMOKED-GLASS PLATE 1014 ELECTRIC RAILWAY JOURNAL [Vol. XLIX, No. 22 on the foundation the vibration of which is to bemeasured. This trough consists of a board 6 ft. longby 6 in. wide with strips on either side. The troughcontains a slide about 3 ft. long by 4 in. wide whichcan be drawn along slowly by means of a winding this slide is attached a strip of smoked glass 3 by 3 in. wide on which the stylus scratches arecord. The principle of the apparatus is that the weightsuspended by the fine flexible wire has sufficient inertiato be unaffected by rapid vibrations and it thereforeremains steady, while the smoked glass plate under-neath moves with the vibrations of the ground on whichit rests. Thus we get a fixed marker writing upon amoving surface. The curves represent the result of twomotions, that of the vibration causing the plate to moveb
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