208 



EARTHQUAKE PHENOMENA. 



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[Sect. VII, 



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do) to the lower end, and below and in a line passin»T 

 vertically through the centre of gravity of the weight fix 

 the stem of a common tobacco-pipe ; let the lower end 

 of this stem just dip into a deep cup filled with pretty 

 thick common ink or other coloured fluid : the action 

 of this needs no description. 



The preceding instruments suffice at once to give the 



direction of transit of the earth-wave and its dimensions ; 

 its rate of progress or transit over the shaken country 

 remains to be observed. 



Several distant observers, with chronometers, will of 

 course best observe this, but such observations cannot be 

 very numerous or extend over a large tract of country ; 

 yet it is most desirable that a network of such observing 

 points should be stretched over the shaken country. For 

 this purpose common house-clocks, situated at several 

 distant points, may be easily arranged, so that the pen- 

 dulum shall be brought to rest and the clock stopped at 

 the moment that the shock passes. 



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