Mineralogy of Sky. 45 



sandstone, marble limestone, schistous limestone, two important 

 members having disappeared in so short a space. This is the only- 

 instance which has occurred to me in Sky of discontinuous strata, 

 since the Western Islands exhibit but few examples of this class of 

 rocks, and I am glad to have an opportunity of mentioning it, as 

 I am convinced that such discontinuities are common in nature, 

 and that great errors have been the result of the fondness with 

 which geologists have pursued through viewless regions of the 

 earth, continuities of strata, and universal formations. But to re- 

 turn to the upper limestone. It is often remarkable for the ca- 

 vernous and corroded aspect which it assumes where In contact 

 with the sea, which arises from the falling out of the shells which 

 it contains. The beds are numerous but irregular, and the shells 

 themselves vary much in quantity in different places. I could find 

 only three species, a gryphite, an ammonite, and a cardlum, nor do 

 I know whether more are contained in them, since but few of the 

 numerous beds are accessible. 



It is now necessary to attempt the tracing of this bed In other parts 

 of Sky, and I Imagine that this can be done to a certain extent. 

 This examination might have been rendered more complete by myself 

 had I commenced the survey of the island in the reverse order to 

 that in which I have described it, being guided for want of a 

 better reason by mere geographical convenience. Hence the re- 

 marks on the distant and solitary fragments of strata, made when 

 there was no prospect of connecting them, are less perfect than 

 they would have been, had I commenced the survey where I have 

 now commenced the description, and they are Insufficient for 

 assigning their general connection. Since however the strata of 

 limestone found at Broadford contain the same animal remains, I 

 have no doubt that they are portions of the same strata, and that 



