of Devonshire and Cornwall. 159 



been empty spaces, and the other, that they have been filled from 

 above. 



I observed the first in the mine of Dolcoath, between Camborne 

 and Redruth, where, at the depth of seventy fathoms below the adit 

 level,* that is to say, according to my observations, one hundred and 

 eighty-four feet below the level of the sea, thei*e was found an 

 empty space in the vein of some fathoms in length, and broad in 

 proportion. The walls of it are smooth, which is seldom the case, as 

 these cavities, called by the miners, druses^ creaks ^ ox pouches^ are 

 almost always lined with crystallisations ; Werner observes, that we 

 find these druses in places where the vein is of greatest thickness. 

 It often very distinctly appears that they have been much longer and 

 wider, but that they have been partly filled up by a new substance 

 having been deposited in them."!" 



The second fact, I have alluded to, I observed in a coal-pit at Littry 

 in Normandy, two leagues S.W. of Bayeux. In sinking the pit 

 St. George, there was found in a vein at the depth of two hundred 

 and fifty feet from the surface, a conglomerate formed of rounded 

 pebbles, the greatest part of them flints, although the saalbande and 

 the rock are of stratified limestone. A branch of a tree was also 

 found, with the ligneous structure preserved, ij: Werner mentions 



* The adit level is twenty-seven fathoms below the surface of the ground, where i\c 

 entrance to the mine is situated, and which is, according to my observations, two hun- 

 dred and thirty-six feet above the level of the sea. 



+ Nouvelle Theorie de la formation dcs filons, p. 80. One of the most singular caverns 

 of this sort, is that which exists at Joachimstal, at the depth of two hundred and fifty 

 toises. This cavern, from which a vast quantity of water ran out, is said to be eleven 

 toises in length and nine in breadth. Its height, which is not yet knov/n, considerably 

 exceeds twelve toises. Ibidem p. 115. 



X Journal do Physique, Mars 1807, p. 225. 



