Reports & Proceedings — Edinburgh Geological Society. 525 



have been an explosion to produce a hole of sufiScient size for the 

 rivers to work in, as the original crater would never liave been large 

 enough; but no great part of the excavation can have been done in 

 this way, since, though the calderas were formed before the out- 

 pouring of the lavas of the third volcanic phase, there is no 

 fragmental deposit at their base, such as must have been produced 

 hj so great an explosion. The forms of the inner slopes are also more 

 in accordance Avith the theory of river erosion. After the initial 

 explosions, then, the cone was breached, either by a lava-fiow or by 

 the cutting back of a stream, and finally carved out to its present 

 shitpe by subaerial agencies. 



XIII. — The Adirondack Intrusives. 

 The Problem of the Anorthosites. By 1^. L. Bowen. Journal of 



Geology, vol. xxv, pp. 209-43, 1917. 

 Stkuctttre of the Anorthosite Body in the Adirondacks. By 



H. P. Gushing. Ibid., pp. 501-9. 

 Adirondack Intrusives. By IS". L. Bowen. Ibid., pp. 509-12. 

 Adirondack Intrusives. By H. P. Gushing. Ibid., pp. 512-14, 



IN the first paper Dr. Bowen discusses the origin of anorthosites in 

 general, with special reference to those of the Adirondacks and 

 of Morin, Ganada. His general conclusion is that anorthosites are 

 produced by the straining off of feraic constituents by gravity from 

 agabbroid magma; at a later stage of the cooling the crystals of 

 more basic plagioclase sink in their turn, forming the anorthosite 

 mass, while the acid residue forms a syenite. The Adirondack 

 complex is thus interpreted as a sheet-like mass with syenite above 

 and anorthosite below. 



In the second paper Professor Gashing expresses his general 

 agreement with Dr. Bowen's views as to the origin of the anorthosites, 

 but dissents from his interpretation of the field relations ; he concludes 

 that the svenite does not form an overlying sheet, but is mainly 

 intrusive into the anorthosite, and the border of gabbro is to be 

 regarded as a chilled margin. The two remaining papers continue 

 the discussion of the points raised in the previous ones. 



R, H. R, 



e,e:fok,ts .A^isriD :E=i?,ooE]E!iDX3src3-s. 



I. — Edinburgh Geological Society. 



March 20. — Dr. M'Lintock, Vice-President, in the Chair. (Issued 

 October 11, 1918.) 



1. "Limits of the Valley Glaciation in the Basin of the Dee." 

 By Dr. Bremner. 



Ijj late Glacial times an ice-stream descended the upper Dee 

 vallej' and, reinforced by affluents from Glenmuick and Glengairn, 

 formed a great valley glacier that extended to a point fully a mile 

 east of Dinnet railway station. The limits of its extension have 



