454 Analyses of Books. [June, 



from Broadford to Loch Eishort. This limestone deposit consists 

 of numerous alternations of limestone, shale, and sandstone, and 

 contains gryphites, ammonites, and belemnites ; it is, therefore, 

 probably the same as the lias of England, and of the N.E. coast 

 of Ireland. In many places these beds are penetrated, and more 

 or less covered by sienite and other trap rocks. Where this is 

 the case, remarkable changes appear to have taken place in the 

 strata, for which no obvious cause exists except the proximity 

 of the trap. The limestone becomes more crystalline, the organic 

 remains become more rare, and where the utmost change has 

 been effected, a perfect granular marble, without any visible 

 organic remains, is the result, not differing in its external cha- 

 racters from that highly crystalline limestone, or marble, which 

 geologists have been in the habit of considering as one of the 

 primary rocks. The sandstone undergoes analogous changes, 

 being converted into quartz more or less compact ; and the 

 shale becoming hard, compact, and brittle, is converted into 

 lydian-stone. 



The limestone deposit is covered by calcareous white and 

 grey sandstone, which at Strathaird is intersected by a multi- 

 tude of vertical dykes of trap without having its stratification 

 materially disturbed. 



The northern and western part of the island, as far as it has 

 been examined by Dr. M. consists chiefly of trap, amorphous, 

 tabular, or columnai', and resembling greenstone in composition, 

 except that augite, instead of hornblende, forms one of its consti- 

 tuent parts. In many places it is amygdaloidal, and contains, 

 besides the more common minerals of the zeolite family, magni- 

 ficent specimens of laumonite and needlestone. On the north- 

 eastern coast it is combined with the lias and other stratified 

 rocks in an infinite variety of ways, the study of which is highly 

 instructive, as it throws much light on many disputed points. 

 " All these irregularities occur in a mass, which, taken in a 

 general view, has the character of a stratified trap, since, not- 

 withstanding these irregularities, it bears a strong parallelism to 

 the already parallel strata with which it is associated. It is 

 abundantly plain that the appearance of stratification in the 

 trap is here the result of the forms of the rocks on which it is 

 placed, or among which it has intruded, in the former case sur- 

 mounting them, and in the latter appearing to alternate with 

 them. The instances of this apparent alternation are highly 

 interesting, from their great extent, as well as from the perfect 

 conviction which they present of the fallacious nature of this 

 supposed connexion. In many cases the alternations of trap 

 are as regular, as decided, and as evenly parallel as those of the 

 stratified rocks themselves, the sandstone and limestone among 

 which it lies. Yet in no instance does it not happen but that 

 at some point or other the alternating bed of trap will detach an 

 intersecting vein, unite itself to the superincumbent, mass, or, 



