. Guide leaflet. izontaland vertical, the range of which may amountto 20 feet or more. The amount of displace-ment will not be recorded by the seismo-graph. It may be determined by resurveyingthe ground. (2) Mbrations will be sst up inthe ground. All earthquakes develop vibrations. Theperiod of the vibrations may vary from afraction of a second in near earthquakes to20 or 30 seconds in distant one seismograph will record all of thesevaried tremors. Due to limitations in con-struction and recording; different types ofinstruments are required for the registrationof near and distan
. Guide leaflet. izontaland vertical, the range of which may amountto 20 feet or more. The amount of displace-ment will not be recorded by the seismo-graph. It may be determined by resurveyingthe ground. (2) Mbrations will be sst up inthe ground. All earthquakes develop vibrations. Theperiod of the vibrations may vary from afraction of a second in near earthquakes to20 or 30 seconds in distant one seismograph will record all of thesevaried tremors. Due to limitations in con-struction and recording; different types ofinstruments are required for the registrationof near and distant earthquakes. A thirdtype of instrument, known as a tromometer,is needed for registering the minute tremorswhich precede and accompany volcaniceruptions. A fourth type of seismograph isrequired for those regions where great earth-quakes occur, for there the motion is apt tobe so strong and vigorous that any machinedesigned for the registration of other typesof earthquakes would be damaged or thrownout of Seismograph The photographs at theleft and below show theseismograph at theAmerican Museum ofNatural History. Therecord which is being ex-amined by the observerbelow records an earth-quake of moderate in-tensity in the ocean bedon August 29, 1934. Soaccurate and sensitiveare these instrumentsthat though thousandsof miles may separatethem from the center ofthe earthquake shock, astudy of the record willoften determine thequakes location
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectnatural, bookyear1901
