88° 23' 



59" 



93° 13' 



10" 



4° 49' 



11" 



5A 0' 



379" 



Oh 19' 



16-8" 



4 n 41' 



21-1" 



4° 43' 



30" 



0° 2' 



8-9" 



Miles. 





256 





76 





84 OLDHAM : THE CACHAR EARTHQUAKE OF IOtH JANUARY 18C9. 



The longitudes of the two stations are respectively — 



Calcutta observatory 



Asalu ... ... ,., . 



Difference 



Local time of shock at Asalu 



Subtract for difference in Long. ... 



Calcutta time of shock at Asalu 

 Time of shock at Calcutta ... 



Difference 

 The distances from the seismic vertical are — 



Calcutta 



Asalu ... ... .., 



180 



So that, to judge from these two observations, the time occupied 

 by the earthquake- wave in passing over a distance of 180 miles 

 could have been 2/ 9", or an average rate of 7,375 feet per second, 

 a velocity which, to say the least, is improbable. 



Of the two observations from which this result has been obtained, one 

 precludes all possibility of error, yet it is difficult to believe that so 

 experienced an observer as Major Godwin-Austin could have made a 

 6erious error in his observations ; * such, however, is the conclusion forced 

 upon us by a comparison of these, the only two observations which 

 can have even the slightest pretence to trustworthiness. 



We are consequently unable to determine, with accuracy, the rate 

 of transit of the wave-form in the case of this great earthquake ; but as 

 there is no reason to suppose that it differed much from what is known 

 to have been the velocity in other earthquakes, this is of little import- 

 ance. 



1 The inaccuracy is probably only in the time of the first shock, and represents the 

 time taken in unpacking the chronometer ; unfortunately we have not any accurate observa- 

 tions of the later shocks besides those of Colonel Godwin- Austin. 

 ( 84 ) 



