256 Dr MacCulloch on the Distribution of Granite 



Hab. West Indies, according to Mr. Dickson. 



This plant, although it has the same habit as the arbusculoid Hooke- 

 r«F, yet possesses no stipules, and has a seta scarcely longer than the 

 pericytial leaves; circumstances which, viewed conjunctly with its 

 other characters, bring this moss so exceedingly near to Neckera den- 

 droides of Musci Exotici, that we are much disposed to look upon them 

 as the same. 



Art. X. — On the Distribution of Granite and of Trap in 

 different Parts of Scotland. By John MacCulloch, 

 M.D. F.R.S.F.L. S. and M.G.S. Chemist to the Board 

 of Orduance, and Professor of Chemistry in Addiscombe 

 College. Communicated by the Author. 



The circumstances in the distribution of granite and of trap, 

 which form the object of this paper, are not only interesting 

 in a o-eological view, but especially deserve the attention of 

 such practical geologists as may be engaged in forming geolo- 

 gical maps of those parts of the country where they occur. 

 To treat of them as fully as they deserve, from their import- 

 ance in both these respects, would require that which is here 

 inadmissible, namely, a geological map of the districts in 

 question, as well as a length of discussion far too great for the 

 present purposes, and which could not indeed well be made 

 intelligible without a very extensive geographical description 

 of the tracts where these appearances are found. 



Although granite exists in many parts of Scotland in con- 

 tinuous tracts of very considerable extent, as in Galloway, in 

 Lorn, in Sutherland, in Perthshire, and in Aberdeenshire ; it 

 is often also found occupying very small spaces, and sometimes 

 in very unexpected situations. In Aberdeenshire, this occur- 

 rence is very common : but it is not there a matter of sur- 

 prise, when the peculiar circumstances attending the stratified 

 rocks of that district are considered. It is easy to perceive 

 that the o-neiss, which constitutes the chief of these, has been 

 destroyed over a great extent of surface, and to a considerable 

 depth ; the earth, and fragments produced from its destruc- 

 tion sometimes remaining in the form of alluvial soil, forming 



