May 23, 1859.] PHYSICAL ENQUIRIES— EARTHQUAKES. 281 



Academy his Memoir on the Dynamics of Earthquakes,* in which 

 his object was to show that all observed earthquake phenomena 

 might be reduced to the direct motions (in accordance with the 

 acknowledged laws of physics and mechanics) of three distinct 

 classes of waves, all produced simultaneously by a single impulse, 

 and originating at a single point, namely : — 1st. The earth wave 

 or shock through the elastic crust of the earth: 2nd. The sound 

 waves through the same, or through the sea and through the 

 atmosphere : 3rd. The great sea waves — or fluid wave of translation 

 which rolls in shore after the shock — to which should be added the 

 liquid wave, which he has denominated the " forced sea wave." He 

 showed that the nature and sequence of the phenomena would differ 

 as the centre of impulse was beneath the land or under the sea ; and 

 in the subsequent parts of his paper, illustrated by diagrams and 

 maps, he indicated the bearings of his theory upon future research 

 and its important connection with vulcanology and terrestrial phy- 

 sics, and thus laid the foimdation for those methods of observation 

 of earthquake phenomena which have since been very widely 

 adopted. He pointed out the necessity for self-registering seismo- 

 meters, and in the same volume of Transactions describes and figures 

 the first completely self-registering seismometer proposed, whose 

 functions were, by the aid of electro-chronographic arrangements, to 

 determine the direction of motion, the moment of transit, and 

 dimensions of the earth wave or shock. Mr. Mallet's views being 

 founded on the admitted laws of exact science, and also distin- 

 guished by their simplicity, received the approbation of many 

 competent judges throughout Europe. f 



In 1850, at the request of the British Association, Mr. Mallet drew 

 up a first Eeport upon the Facts of Earthquakes, J in which he dis- 

 cusses all anterior views, and with the guidance of his theory 

 classifies and separates imder distinct propositions the facts found 

 scattered in multifarious confusion through earthquake narratives. 

 He concludes by enunciating certain desiderata, amongst which 

 were the formation and discussion of a complete catalogue of earth- 

 quakes for all time and all countries, and by submitting to the 

 actual test of experiment the views which he had theoretically an- 

 nounced as to the elastic transit of the earth wave. 



Funds were placed at his disposal for the purpose by the British 



♦ Trans. R. I. A., vol. xxi. p. 1. 



t See Mrs. Somerville's ' Physical Geography/ Humboldt's * Kosmos,' &c. 



X Trans. Brit. Assoc. 1850. , 



Y 2 



