798 THE JOURNAL OF GEOLOGY. 



has here a steeper hade, so that the older dolomite has been car- 

 ried only a short distance over the newer beds. 



Metamorphism along the fault. — Of considerable interest is the 

 recrystallization which has taken place along the fault plane. The 

 tremolite of the Housatonic ridge, and the large pyroxene crys- 

 tals of the east base of the Cobble at South Canaan, must be 

 explained in this way. The ragged quartzitic dolomite rock 

 which characterizes the Housatonic ridge throughout its entire 

 extent and is not found elsewhere in the region, is believed to 

 owe its characters to a crushing along the fault and a recementing 

 of the fragments by a vein quartz — it is in other words, a fault 

 breccia. 



In the vicinity of the great thrust planes of the Northwest 

 Highlands of Scotland, which have been so carefully studied by 

 Geikie, Peach and Home, and their associates of the Geological 

 Survey of Scotland 1 , schistose structure and new minerals have 

 been developed by the shearing, micas, hornblende, actinolite 

 and garnet being produced in this way 2 . Another instance of 

 this sort is furnished by the overthrusts of the Rocky Mountains 

 along the line of the Northern Pacific Railway. 3 These thrusts 

 have likewise produced metamorphism of the beds along the 

 thrust planes, argillaceous layers being made schistose and lime- 

 stones being whitened and cracked. 



Thickness of the Egremont Limestotie. — In the Mt. Washington 

 paper, I have shown that the thickness of the Egremont Lime- 

 stone in the southern portion of the summit plain is less than 

 one hundred feet, and that a little farther south it probably dies out 

 altogether. In the northern portions of that area, where it 



1 The Crystalline Rocks of the Scottish Highlands, by Arch. Geikie, B. N. Peach, 

 and John Horne. Nature, Vol. XXXI., pp. 29-35, Nov., 1884. 



Report on the Recent Work of the Geological Survey in the Northwest Highlands 

 of Scotland, Based on the Field Notes and Maps of Messrs. B. N. Peach, J. Horne, W. 

 Gunn, C. T. Clough, L. Huxman, and H. M. Cadell. Communicated by A. Geikie. 

 Quart. Jour. Geol., Soc, London, Vol. XLIV., pp. 378-441, 1888. 



2 Nature, Vol. XXXI, p. 35. 



3 Report on the Geological Features of a Portion of the Rocky Mountains, by R. G. 

 McConnell. Ann. Rep. Geol. Surv. Canada, (New Series) Vol. II., 1886, p. D34. 



