BY THE REV. W. B. CLARKE, M.A., F.G.S., &c. 273 



epidote as a very common mineral under similar circumstances 

 of transmutation. Epidote is included by Delesse in the same 

 division of minerals formed in rocks by transformation, as garnet. 

 Most of these minerals when found in calcareous rocks, have 

 been silicated. Chiastolite also occurs in slates over granite on 

 Jejedzric Hill in Maneero. 



When sandstones come in contact with granite rocks, they 

 are frequently converted into quartzite, producing metallisation, 

 silicification and vitrification. A true quartzite may according 

 to Delesse always be distinguished by the occurrence in it of mica. 



It can scarcely be doubted that the silica has often been ad- 

 ministered by silicated waters or springs, under the action of 

 transmutation by Imbibition which has gradually produced the 

 observed changes. 



In some instances these springs may be almost proved to 

 have been poured forth on the ancient sea margins ; for, in 

 certain places a number of marine shells that belong to shallow 

 water, have been found silicified wholly or in part, as is noticeable 

 in some of the Jurassic formations, but notwithstanding this, no 

 one, it seems, has found a silicified Ammonite ; though occasion- 

 ally Ammonites and Belemnites occur unsilicified amidst silicified 

 shells. The explanation is, that the Cephalopods being inhabi- 

 tants of deep water were not exposed to the influence of the silica 

 so freely administered near the shore ; and after mineralisation in 

 another way, may have drifted to the shallower depths. Perhaps, 

 however, some fossils have been silicified under a more perfect 

 power of assimilation than others : for, in various Spirifers I have 

 found what must have been a tendency to resist or to accept sili- 

 cification in some parts of their organization more than in others. 

 Thus, frequently the spiral appendages have been silicified, whilst 

 the rest of the animal was transmuted by calcareous agency. 



Respecting Granite itself, it appears to undergo a transmuting 

 action. I am one of those who deny the occurrence of what is 

 termed primitive granite. If such exists, I believe no human eye 

 ever beheld it. The researches of Yirlet and Scherer demon- 

 strate, that the crystalline structure of certain granites surpasses 

 altogether the limits of granite, i. e. the facts which belong to the 

 different materials are such as frequently to contradict all con- 



