ISLE OF MAN. GEOLOGY. LIMESTONE. 565 



tified, consists of one deposit, or of one series, as is 

 proved by its continuity, and by the identity of the organic 

 remains. The absence of the stratified disposition is there- 

 fore no proof that any given limestone does not belong 

 to the class of the secondary rocks, a conclusion equally 

 deducible from the history of the calcareous district of 

 Sky. There is consequently no reason a priori why a 

 limestone of even much more recent formation than this 

 should not be found unstratified . 



The absence of organic remains proves nothing respect- 

 ing the comparative antiquity of limestone, and the crystal- 

 line texture is also an imperfect criterion of the geological 

 relations of any given mass of that substance ; deductions 

 which are equally to be made from the same example. 



There appears no definable limit of the extent to which 

 a limestone, really secondary, may exist in an unstratified 

 state; and the various unstratified limestones which have 

 been described in different parts of the world, as of a 

 period prior to the secondary rocks, require therefore 

 to be re-examined ; excepting those which alternate with 

 gneiss, micaceous schist, quartz rock, or argillaceous schist. 



Some of these conclusions will, in a practical view, be 

 equally valuable, whether the limestone be supposed to 

 have been originally formed in the mixed manner in which 

 it now appears, or to have undergone the change from the 

 stratified disposition to the unstratified, in consequence 

 of posterior alterations. 



It is now necessary to remark that the confusion of 

 structure here described, appears hitherto to be limited 

 to limestone, a circumstance which may suggest the 

 explanation that has already been indicated by the corre- 

 sponding facts formerly stated, namely, that it is the result 

 of the fusible nature of that rock. Nor is it possible 

 to avoid remarking the analogy which exists between this 

 case, and those formerly noticed, where masses of trap are 

 to be found intimately associated with schistose rocks, 

 as in the hill of Kinnoul, and entangling fragments which 



