. Earthquakes and other earth movements . A^ 3 Fig. 3. In an instrument called a double-bracket seismograph, invented by Mr. Gray, we have two brackets hinged to each other, and one of them to a fixed frame. The planes of the two brackets are placed at right angles, so as to give to a heavy mass supported at the end of the outer bracket two degrees of horizontal freedom. In all bracket machines, especially those which carry a pivoted weight, it is doubtful w^hether the weight pro- vides a truly steady point relatively to the plate on which the record is written for motion parallel to the direc
. Earthquakes and other earth movements . A^ 3 Fig. 3. In an instrument called a double-bracket seismograph, invented by Mr. Gray, we have two brackets hinged to each other, and one of them to a fixed frame. The planes of the two brackets are placed at right angles, so as to give to a heavy mass supported at the end of the outer bracket two degrees of horizontal freedom. In all bracket machines, especially those which carry a pivoted weight, it is doubtful w^hether the weight pro- vides a truly steady point relatively to the plate on which the record is written for motion parallel to the direction of the arm. Parallel-motion Instrument—A machine which writes its record as two components, and which promises great g stability, is one suggested by Professor C. D. West. Like the bracket machines it con- sists of two similar parts placed at right angles to each other, and is as follows: A bar of iron A is suspended from both sides on pivots at C C by a system of light arms hinging with each other at d e <•'! S m a I I Fig. 4.
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Keywords: ., bookcentury1800, bookdecade1880, bookpubl, booksubjectearthquakes
