314 MK. J. B. HILL ON THE [Aug. I9OI, 



observed in this conglomerate-deposit by my colleagues, no such 

 boulders had then been detected by me in that part of the deposit 

 which is located in the Loch Awe Basin. Since the date of that 

 paper, however, Mr. H. Kynaston, while continuing the examination 

 of this deposit, has completed the chain of evidence by discovering 

 similar foreign boulders in the latter area. My argument, therefore, 

 in so far as it was based on the continuity of the Highland Boulder- 

 bed, remains valid, notwithstanding that crush-conglomerates may 

 have been mistaken for the former in some of the localities cited 

 by me in that paper. 



The object of the present communication is not only to extend 

 my former description of the Loch Awe area, and to record the 

 occurrence of crush-conglomerates in the Highlands of Scotland, 

 but to enforce the deductions of Mr. G. W. Lamplugh, by insisting 

 that these pseudo-structures have a more prominent position in rock- 

 building than their recorded occurrences would lead us to suppose. 

 In areas like that described by Mr. Lamplugh in the Isle of Man, 

 and by myself in Cornwall, elucidation of these phenomena requires 

 a longer and more intimate acquaintance with local geological 

 structures than the ordinary observer cares to acquire, and descrip- 

 tions, however lucid, may fail to carry conviction where direct 

 proof is wanting. In Argyllshire, fortunately, the case is different, 

 as I am able to demonstrate that boulders of the crush-conglom- 

 erates are of later age than the matrix in which they lie, an argu- 

 ment from which the most sceptical mind will find escape difficult. 



II. GejS'eeal Desceiption of the Aeea. 



The area in Argyllshire in which these crush- conglomerates have 

 so far been detected, comprises a small belt of country to the south- 

 west of Loch Awe, of about 10 square miles ; but as the Survey 

 progresses they will probably be found to occupy a more extended 

 horizon. 



Before entering into a discussion of these structures it will be 

 necessary to give a brief outline of the rocks which make up the 

 district, more especially of those in which these characters are 

 displayed. 



The sedimentary rocks met with include all the members of the 

 Loch Awe Series, consisting of grits, slates, and limestones, with 

 which are associated enormous masses of igneous material of Dal- 

 radian age, ranging in composition from intermediate, to basic, 

 while dykes of porphyrite, of later date (probably of Old Eed Sand- 

 stone age), are occasionally met with. Finally, a plexus of Tertiary 

 dykes of basaltic type traverses the country in a north-westerly direc- 

 tion, at right angles both to the strike of the sediments and the 

 foregoing igneous rocks associated with them. 



The members of the Loch Awe Series call for no detailed descrip- 

 tion, their characters having been described in my former communi- 

 cation to this Society.^ 



1 Quart. Journ. Geol. Soc. toI. Iv (1899) pp. 470-92. 



