354 SKY. GEOLOGY. SECONDARY STRATA. 



The organic remains of Rasay have been shown to re- 

 semble those of Somerset and Gloucestershire, and they 

 determine the series in that island to be analogous to 

 the lias of the English strata. Even without this evidence, 

 the limestone of Trotternish, with its accompanying shale 

 and sandstone, exactly resembles many of these beds 

 as they are found in England and Ireland, between which 

 latter and the Western islands of Scotland there are 

 some strong points of correspondence. It will hereafter 

 be seen, in examining the general connexion of all 

 these islands, that portions of the same series are found 

 scattered throughout the whole ; extending thus the 

 boundaries of a formation which has been found in other 

 parts of Europe. 



We are not at present acquainted with all the marks 

 that distinguish the limits of this series, nor is it by 

 any means certain that our knowledge of organic fossils 

 is sufficient for this purpose ; were it even proved that 

 there is a constant and inviolable relation between one 

 series of rocks and one set of fossil species. Under 

 these circumstances it may be questioned whether the 

 gryphite limestone of Strath appertains to the lias ; 

 yet geologists will perhaps consider it the lowest part 

 of this series. If this be established, the lias here reposes 

 immediately on the primary rocks, to which I have 

 shown the red sandstone to belong; the intermediate 

 strata, which occur in England and in other places, 

 being absent. Such irregularities are too well ascertained 

 to be now any longer subjects of doubt; and they will 

 confirm to geologists the propriety of limiting their 

 conclusions respecting the continuous nature of the rocks 

 that occupy the earth's surface. 



Before proceeding to the unstratified rocks which 

 constitute the remaining and larger part of this island, 

 it is necessary to describe some stratified substances 

 connected with those that have already passed under 

 review, but which being of an incidental nature could 



