KARTH^UAXES. 190 



to pass from link to link along the chain of phenomena until 

 it leaches the period when, in the solidifying process of our 

 planet, and in its first transition from the gaseous form to the 

 agglomeration of matter, that portion of the inner heat of the 

 earth was developed, which does not belong to the action of 

 the Sun. 



In order to give a general delineation of the causal con- 

 nection of geognostical phenomena, we will begin with those, 

 whose chief characteristic is dynamic, consisting in motion 

 and in change in space. Earthquakes manifest themselves by 

 quick and successive vertical, or horizontal, or rotatory vibra- 

 tions.* In the very considerable number of earthquakes 

 which I have experienced in both hemispheres, alike on land 

 and at sea, the two first-named kinds of motion have often 

 appeared to me to occur simultaneously. The mine-like explo- 

 sion the vertical action from below upwards was most strik- 

 ingly manifested in the overthrow of the town of Riobamba 

 in 1797, when the bodies of many of the inhabitants were 

 found to have been hurled to Cullca, a hill several hundred 

 feet in height and on the opposite side of the river Lican 

 The propagation is most generally effected by undulations in 

 a linear direction,! with a velocity of from twenty to twenty- 

 eight miles in a minute, but partly in circles of commotion 

 or large ellipses, in which the vibrations are propagated 

 with decreasing intensity from a ceirtre towards the circum- 

 ference. There are districts exposed to the action of two 

 intersecting circles of commotion. In northern Asia, where 

 the Father of History,^ and subsequently Theophylactus 

 Simocatta, described the districts of Scythia as free from 

 earthquakes, I have observed the metalliferous portion of the 

 Altai mountains under the influence of a twofold focus of 



* [See Daubeney, On Volcanoes, 2nd ed., 1848, p. 509.] TV. 



t [On the linear direction of earthquakes, see Daubeney, On Volca- 

 noes, p. 515.] TV. 



* Herod., iv. 28. The prostration of the colossal statue of Memnon, 

 which has been again restored, (Letronne, La Statue vocale de Memnon, 

 1835, pp. 25, 26,) presents a fact in opposition to the ancient prejudice 

 that Egypt is free from earthquakes (Pliny, ii. 80) ; but the valley of the 

 Nile does lie external to the circle of commotion of Byzantium, the 

 Archipelago, and Syria (Ideler ad Aristot. Meteor., p. 584). 



Saint- .Martin, in the learned Xotes to Lebeau, Hist, da Bus Empire, 

 iU. p 401. 



