Show THE seismograph instrument WHICH gelbs OP earthquakes every movement of the earth Is ac curatelo cura tely recorded at washington Office Record of san bran cisco earthquake if science has not as yet discovered any method by which the coming of an earthquake can be foretold it na perfected a delicate instrument which with the utmost accuracy tells the story of the vibrations when the do occur this Is the seis mcgraph and the record which it haa left of the re at upheaval at san francisco has occupied the attention of scientists since then and drawn the eyes of the general public to the in strument ment itself and people are asb ng what the aph Is like and now it works it seems wonderful that an inspru ment located at washington could be able to record the earthquake at san francisco but such Is the case in tact no vibration of ane earth surface any where on the glebe however slight goes unnoticed oy this sensitive little earthquake up to the time of the upheaval which leveled the pa coast metropolis the de icat needle of the u mcgraph mo graph had been tracing long sti tight white lines on the surface of the record shet morning when it suddenly becam agitated at eight clock 19 minute and 20 seconds and began to make more or less elon gated waves U 8 25 clock the strong waves bean and the recording needle moved back and forth across the shee then followed the most violent wives between i 32 ani 8 35 clock enty fifth merld lar time as Is shown by the record at one time the antion of the needle wa so vigorous thai its point went off the sheet which it kept in motion bi a clock machin and the point did no return to the sapet until there wa s secondary lull n the great dist rb ance then when the needle had re fumed its the earth alons and waves fontin ed until I 1 05 when the agitations cease 1 each of the baes on the reco d shee represents an do u of time the of the shet keep ng time with the tick of the connected clod the units of time are marked on thib heet which is coverd with gelatine an thus the observer Is enabled to tell just when the earthquakes bean an when they end d by the nar la made by the nee tie point this instrument which io said td be one of the finest in the world was in stalled by prof willas L moore chie of the united S ates weather b irea i and Is anler the immediate contro and supervision of the earthquake or seismographic chiv ion of the bureau prof F marvia is head of this di vision and sin e the in anc disaster has sho and described the instrument to abny visitors it i installed in a basement apartment THE seismograph away under the weather bureau build ing tar removed from the noisy hurly burly of the and is practically all a mechanical recluse this instrument Is of a very su type and gives an accurate rec ord of the movement of the earth al the pendulum in the hon plane the mechanical principles in the construction of a seismograph of this type were first developed anc applied to the measurement of earth quakes in the latter part of 1880 james A ewing then professor of me cb anical engineering at the university of boklo but now professor of ism and applied mechanics at the uni hersity of cambridge england nu berous modifications have since been incorporated in the instrument by gray and others and in it present form it Is well adapted tc measure and record all kinds of earth quakes except perhaps the most de ani Is especially suited to register the feeble unfelt earthquake which frequently occur in all parts ot the world the instrument in the basement room 0 the weather bureau is in stalled on depante castings secured to thick blocks of stone cemented firmly into the concrete floor of the building and projecting but a few inches above the floor level the foundation of the instrument Is separate from the build ing being far down in the earth so that it will not be affected by arti disturbances the extreme sensitiveness of the se Is shown in the following statement made by prof marvin the extreme sensitiveness to tilting Is ex in several ways the weight of the observer almost anywhere on the floor of the small room in which the instrument Is installed suffices to tilt the pendulum enough to show on the record a large displacement displace men is produced by standing at one side of the pedestal |