PROPOSED FORM OF SEISMOGRAPH 



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substantially at rest, while the movement is communicated directly to the 

 frame-work and paper, which thus moves under the tracing point. 



(4) The instrument suggested consists of a mass of metal resting on rollers 

 or steel balls, and connected by a thin steel band to a sheet metal diaphragm. 

 This diaphragm forms one boundary of a cell containing water or some other 

 liquid, and is furnished on the opposite side with pipe connection and vertical 

 glass tube. The cell is securely attached to a base plate, and thus to the earth, 

 and hence must share in whatever movement may be imposed on the earth at 

 this point. Through the connection with the diaphragm such movement will 

 also be imposed on the mass of metal referred to (except for the slight yield of 

 the diaphragm), and thus we have a known mass whose motion must neces- 

 sarily be a close copy of the actual earth movement. This imposed oscillatory 



Figure 1. — Proposed Form of Seismograph 



motion will develop forces due to the acceleration and retardation of the mass 

 of metal, and these forces will give rise to minute displacements of the dia- 

 phragm. These movements by the method indicated may be multiplied one 

 thousand fold or more, and thus made visible as a rise and fall of the liquid in 

 the tube. 



(5) Various means might be employed for registering either the maximum 

 excursion of the liquid or of obtaining a complete registration. These are mat- 

 ters of detail not fully worked out and not important, so far as the main prin- 

 ciple of the apparatus is concerned. 



(6) The instrument may be made more or less sensitive by varying the thick- 

 ness of the diaphragm and the diameter of the tube. With easily realized 

 dimensions an ordinate of 3 or 4 inches may be obtained with not to exceed 

 .002 or .003-inch movement of the diaphragm. 



(7) By calibration the actual forces in play corresponding to any change in 

 level of liquid are easily determined, and such forces expressed as percentages 



