488 MR. J. B. HILL ON PEOGEESSIVE METAM0RPHI8M [Aug. 1 899, 



we are dealing with the unaltered sediments of Loch Awe or their 

 extension into crystalline schists to the eastward. The Boulder- 

 hed, although not a continuous deposit, makes its appearance here 

 and there across the Highlands from near Braemar on the east to 

 Islay on the west. Along this belt of country it has a fairly definite 

 stratigraphical position. It always occurs in the series referred 

 to in the present paper as the Loch Awe Series, but it may occur in 

 different members of this division. Its most general position is in 

 the quartzite member of the Loch Awe Series, but in Argyllshire it 

 has also been met with in the limestones and black-schist members 

 of that series. My colleague, Mr. G. Barrow, informs me that in 

 the Schiehallion area of Perthshire the Boulder-bed is made up 

 almost entirely of large boulders of granite. In the area far to the 

 south of Braemar the pebbles are smaller and still mostly igneous, 

 while 4 miles south of Braemar the bulk of the pebbles are sedi- 

 mentary. In the Loch Awe area the Boulder-bed has been observed 

 in many localities within the Loch Awe Series and in every division 

 of that series. The area lying between Glen Aray and Loch Awe 

 in a belt passing Cruach Mhor contains numerous exposures 

 of it. Along this horizon the matrix in which the boulders are 

 embedded varies in different localities, and may consist of every 

 member of the Loch Awe Series from grits, quartzites, dark schists, 

 to the typical Loch Awe Limestone. A few of the localities are 

 recorded below : — 



1 mile east of Cruach Mhor, boulders of quartzite 6 inches 

 and more in length, in a dark schistose matrix. 



2 miles north-west of Cruach Mhor, quartzite-pebbles 

 up to 2 inches in length, in a matrix of limestone. 



2j miles west of Cruach Mhor, boulders of grit 1 foot 

 long, in a dark quartzose-argillaceous matrix. 



3^ miles south-west of Cruach Mhor, boulders and 

 pebbles of blue compact limestone and pebbles of blue slate, in a 

 matrix of crystalline limestone. 



5 miles south-west of Cruach Mhor, boulders of com- 

 pact limestone up to 1 foot in length and small quartzite-pebbles, 

 in a matrix of typical Loch Awe Limestone. 



In the same district there are various localities where boulders of 

 grit and quartzite occur, in a matrix of a composition similar to that 

 of the boulder. 



On the west side of Loch Awe examples of the Boulder-bed 

 are equally common. Still farther west, in Islay, my colleague, 

 Mr. Wilkinson, has described a similar Boulder-bed where, as noted 

 by Mr. Barrow in various districts of Perthshire, some of the 

 boulders are of foreign material. 



The occurrence of foreign boulders, and of boulders of material 

 different from the matrix, makes it quite clear that we are dealing 

 with a regular sedimentary deposit, and that it does not owe its 

 origin to movements such <is have given rise to crush-conglomerates. 

 And the position of this Boulder-bed among sediments of similar 

 nature across so large a portion of the Highlands may be regarded 



