342 ME. G. BAEROW ON THE OCCUREENCE OF [Allg. T9OI, 



discussed the rocks affected by wliat is commonly known as regional 

 metamorphism have been driven over a newer series by a movement 

 of pre-Old Red Sandstone age, and no similar movements have since 

 taken place in this area. But on the margins of crystalline areas in 

 other countries similar movements have taken place as late even as 

 Tertiary times, and in such areas a Tertiary age has been claimed 

 for the regional crystallization. In view of our experience both in 

 the Northern and Southern Highlands, it seems not unreasonable to 

 suggest that movements similar to those here described may have 

 occurred along the slightly crystalline margin of the areas affected 

 by regional metamorphism. Whatever may be the age of the beds 

 overridden by the crystalline schistose rocks, there will appear to 

 be a passage from the newer into the older, and the crystallization 

 of both will seem to be somewhat later than the age of the beds so 

 overridden. As in the case of the area here described, the transition 

 from one series to the other may be deceptive. 



YI. The Mechanical Deformation of the Silurian [?] Rocks. 



I cannot conclude the account of the phenomena seen in these 

 lenticles without some notice of their bearing on the vexed question 

 of the origin of crystalline schists. Great as is the crushing and 

 shearing in these lenticles, it has nowhere resulted in the production 

 of a crystalline schist, and not a particle of new brown mica has been 

 met with anywhere. The total length of outcrop of more or less 

 basic igneous rock is about 10 miles. 'No hornblende-schist ever 

 occurs in it. Indeed, it would be difficult to find an area which 

 seems to show so conclusively that mechanical deformation alone does 

 not produce crystalline schists. The structures in the sheared grits 

 are in the main identical with those seen in the Torridon Sandstone 

 of the jN'orth-western Highlands,^ and in the Boulder-Conglomerate 

 found by my colleague, Mr. G. W. Lamplugh, in the Isle of Man.^ 



YII. Summary of Results. 



The results of the examination of the remarkable group of rocks 

 described in this paper, which intervene between the Highland 

 Schists and the Old Red Sandstone in Forfarshire and Kincardine- 

 shire, may be summarized as follows : — 



(i) They may be arranged in two divisions — (a) the Jasper and Green- 

 Rock Series, and (6) the Margie Series. The former is most 

 probably of Arenig age, and the latter is of later date, though 

 undoubtedly of pre-Old Red Sandstone age. 



(ii) Both groups of rock have been much deformed, the shearing 

 being most persistent along the junction of the Highland 

 rocks with the northern margins of the supposed Silurian 

 rocks. 



' Quart. Journ. Geol. Soc. vol. xliv (1888) pp. 431 et seqq. 

 2 Ibid. vol. li (1895) p. 5ti3. 



