Mr. Mallet's Notice of the British Earthquake of November 9, 1852. 403 



In the preceding columns the directions, where given, are those of true me- 

 ridian. The times of shock (as in map) are Greenwich mean time in Great 

 Britain (except as to Congleton); and in Ireland, assumed Dublin time. Most 

 of the newspaper correspondence adopted was authenticated. The names of 

 private correspondents are not in all cases given ; and their information must 

 be taken on the author's authority. 



The more important points to arrive at in every earthquake, of course, are: — 



1. The direction of emergence of the earth-wave of shock. 



2. The moment of its emergence in time. 



3. Its velocity of emergence. 



4. The dimensions of the wave, or rather its altitude at each point of ob- 

 served emergence. 



In the present instance the observations collected afford but a very meagre 

 basis even for approximate answers to any one of these inquiries, and such 

 must- ever be the case until self-registering seismometers are to be found in all 

 our observatories, &c. 



The following conclusions, however, are justifiable: — 



1. The general direction of emergence of the earth-wave was from south 

 to north, making a considerable vertical angle with the horizon, i. e. emerging 

 upwards from the ground. 



The following is some of the evidence that it had both a horizontal and a 

 vertical component of motion. As regards horizontal direction (that which is 

 commonly best observable, and popularly assumed to be the only element of 

 direction), there is abundant testimony that it was from south to north, varying 

 more or less to the eastward or westward. There is also the decisive evidence 

 of the fall of a pocket telescope to the northward, which stood on end in a glass- 

 case in Mr. Yeates' optician shop, in Graftou-street. Its fall towards the north 

 does not invalidate the other evidence that the primary motion was from south 

 to north; as there exist numerous observed cases of objects disturbed by the 

 primary or forward movement of the earth-wave, and thrown dovm by its return 

 movement. (See First Report on Earthquakes, Trans. Brit. Ass.) 



As respects the vertical component, in addition to the testimony of many 

 vrhofelt an up and down movement, the conditions of fall of the picture in the 

 author's premises, already noticed, afford conclusive evidence. The wall against 

 which it hung ranged nearly east and west ; a shock coming horizontally, or 



VOL. xxu. 3 G 



