assumed to accompany Earthquakes. 539 



The other two were twisted off from the wall in a north-east- 

 erly direction, and left standing." The direction of the shocks 

 was thought to be either from the south-west, or from the 

 north-west. 



We shall see hereafter evidence in the twisting of the two 

 remaining buttresses, that the former was the real direction 

 of the shocks, and that there was no vorticose motion, (indeed, 

 the idea of two vortices, with centres only a few feet apart, is 

 absurd upon the face,) but that the twisting of the buttresses 

 is accounted for simply by a straight line movement, in con- 

 nection with the attachment of the buttresses at one side, to 

 the flank wall of the church. 



The last instance I shall quote is from the pages of the able 

 and delightful Darwin, in his Journal of a Naturalist's Voy- 

 age (Colonial Library, edit. p. 308), in describing the effects 

 of the great earthquake of March 1835, upon the buildings 

 in the town of Conception ; and after noticing, also, the evi- 

 dences of immense velocity in the shock, by which the pro- 

 jecting buttresses from the nave walls of the cathedral had 

 been cut clean off close to the wall, by their own inertia, while 

 the wall, which was in the line of shock, remained stand- 

 ing; he proceeds, — "Some square ornaments on the coping 

 of these same walls were moved by the earthquke into a dia- 

 gonal position. A similar circumstance was observed after 

 an earthquake at Valparaiso, Calabria and other places, in- 

 cluding some of the ancient Greek temples " (for which he 

 quotes Arago, in Ulnstitut. 1839, p. 337, and Miers's Chile, 

 vol. i. p. 392). 



"This twisting displacement," he proceeds, "at first ap- 

 pears to indicate a vorticose movement beneath each point, 

 thus effected ; but this is highly improbable. May it not," 

 he adds, " be caused by a tendency in each stone to arrange 

 itself in some particular position with respect to the lines of 

 vibration, in a manner somewhat similar to pins on a sheet of 

 paper when shaken ?" 



The sagacity of Darwin at once showed him that the vor- 

 ticose hypothesis was most improbable, and that to order to 

 its being able at all to account for the phaenomenon, a sepa- 

 rate vortex must be admitted for every separate stone found 

 twisted, the axis of rotation of the vortex having been coinci- 

 dent with that of the stone: besides this paramount improba- 

 bility, therefore, a little further reflection would have led either 

 Lyell or Darwin to estimate the necessarily inconceivable ve- 

 locity of motion, at the extremity of the radius of one of these 

 vortices, even if assumed at no more than a few hundred feet, 

 in order that its velocity, within a few inches of the centre, 



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