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Sect, VIL] 



EARTHQUAKE PHENOMENA 





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iBures, caY 



ties, wells, &c. 

 oil land ; of mineralized or fouled water suddenly made 



so ; of gases evolved from 



Where possible, 



immediate chemical qualitative examination should be 



made. 



Specimens in particular should be brought home of the 

 rocks or other mineral masses through which the speed of 

 transit of the earth-wave has been carefully observed, 

 such as will enable the modulus of elasticity/ of the mass to 

 be determined. Where this is rock, three specimens 

 should be taken of maximum, minimum, and average 

 hardness, density; and compactness, as representatives of 

 the whole shaken district, noticing especially in stratified 

 rock the depth from surface of ground and from top of 

 the formation at which taken : each specimen to be of a 



r-_. 



size enablin 



least 



feet in length by four inches square. Where convenient, 

 this operation may be done on tiie spot. Where the dis- 

 trict is a deep detrital or alluvial one, the depth and 

 characters of the loose materials should be carefully 

 observed, and illustrative specimens, as far as possible, 

 brought home. 



Collateral conditions to be observed are — ^barometer be- 

 fore, during, and after the earthquake ; thermometer, rain- 

 gauge ; hydrometer and electrical state of the air during 

 the phenomena ; magnetometrical observations where these 

 are practicable ; all unusual meteorological appearances to 

 be noted ; the state of tide at time of each shock ; the rise 

 and fall of tide at the place ; and any tidal anomalies 

 produced after the earthquake. Active volcanic phe- 



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