t^ 



•XlV 



H of ^' H 



S 



^ 



It.,, %! 



ino 



"^H loff 



"^^ of raUers 



D80 



■V livincr 



AXD CAVES. 



n that many 

 ned in certain 

 i which are 



r. 



the sea ; ^ 



w^ with rent^' 



..♦ ,,ie 



-iflti 



.!le thei^ 



to 







le 



,!,# 



J 



N 



^ 



^. 



I 



I 



i 



Ch. xlv. t 



ALLUVIAL DEPOSITS AND CAVES. 



515 



manj 



is no less than ten acres in area, and 150 feet in its greatest 

 height. Besides the principal series of ' antres vast,' there 

 are a great many lateral embranchments not yet explored."^ 



The cavernous structure here alluded to,' is not altogether 

 confined to calcareous rocks ; for it has lately been observed 

 in micaceous and argillaceous schist in the Grecian island 

 of Thermia (Cythnos of the ancients), one of the Cyclades. 

 Here also spacious halls, with rounded and irregular walls 

 are connected together by narrow passages or tunnels, and 

 there are many lateral branches which have no outlet. A 



some 



the whole, and left a 



m 



the floor; but the erosive action of the stream 



clay upon 



supposed to have given rise to the excavations in the first 

 instance. M. Virlet suggests that fissures were first caused 

 by earthquakes, and that these fissures became the chimneys 

 or vents for the disengagement of gas, generated below by 

 volcanic heat. Gases, he observes, such as the muriatic, 

 sulphuric, fluoric, and others, might, if raised to a high 



decompose the rocks which they 



temperature, alter 

 traverse. There are sisms 



rmer action of such 

 vapours in rents of the micaceous schist of Thermia, and 

 thermal springs now issue from the grottos of that island. 

 We may suppose that afterwards the elements of the decom- 

 posed rocks were gradually removed in a state of solution by 

 mineral waters ; a theory which, according to M. Virlet, is 

 confirmed by the effect of heated gases which escape from 

 rents in the isthmus of Corinth, and which Have greatly 



When 



we reflect on the quantity of carbonate of lime 

 annually poured out by mineral waters, we are prepared to 

 admit that large cavities must, in the course of ao-es be 

 formed at considerable depths below the surface in calcareous 



rocks, t 



-i- 



remembered, are at once 



more 



^Nahum Ward, Trans, of Antlq. Soc. 

 of Massachusetts, Holmes's United 

 States, p. 438. 



T. L 2 



t Bull, de la Soc. Geol. do Franc?, 

 torn. ii. p. 329. 



t See above, Vol. I. p. 401. 



