362 B. K. Emerson— " Bernardston Series" of 



of 1,200 feet above the sea-level, the Brazos in the same lati- 

 tude has cut down to within 600 feet of the sea-level in its soft 

 bed. 



This fact has given the Brazos a great advantage over its 

 competitor, the Colorado, for drainage territory ; and this, in 

 the battle for conquest of headwater drainage area, has enabled 

 the Brazos to push the divide close up to the Colorado in terri- 

 tory, which, under more favorable circumstances, should belong 

 to the latter stream. The side streams of the Brazos having a 

 much lower plane to which it was possible to base level the 

 drainage area than those of the Colorado had were much more 

 powerful agents of erosion ; and the result is that a tributary 

 to the Colorado from the east is rarely 10 miles long, while 

 Brazos tributaries, heading in the same divide, flow fully 75 

 miles before emptying into their mother stream. 



Art. XL VI. — A descrip>tion of the "Bernardston Series" 

 of Metamorphic Upper Devonian Rocks / by Ben K. 

 Emerson. 



[Continued from p. 275.] 



The position and extension of the basal quartzite was the 

 first clue to the complex stratigraphical arrangement of the 

 series in its eastward continuation. Beginning at the point 

 already described, east of the road to East Mountain (back of 

 "Mrs. Haley's" on the map), with a strike due east, it has 

 bent round to TT. 65° E. before it goes under the massive drum- 

 lin which lies east of the river, and on its emergence, it is- 

 abundantly exposed, with the same strike, along the .southern 

 of the two northwest roads mentioned above, especially south 

 of A. G. Chapin's house. Taking the direction of this road 

 across the valley of Dry brook, it can be followed readily, with 

 the same strike and low S.E. dip and physically unchanged, 

 through the chestnut woods N". W. of the end of Purple's blind 

 road, crossing the first north and south road in Northfield, 

 where a loop of the brook crosses the road ; and gradually 

 bearing round to the north, it crosses the State line with a 

 strike 1ST. 10° W. 



(i) The quartzite conglomerate. — Back of Mrs. Haley's, on 

 the Eall River road, and just east of the Williams farm, across 

 the valley, ledges of the rock appear, and it outcrops abund- 

 antly along the second road running east from the Fall River 

 road (A. G. Chapin's) to its end. Where the road begins it is 

 an obscurely bedded conglomerate of quartz pebbles, in a dark 

 paste containing much slaty material. The conglomerate here 

 toward its base is exactlv like the same rock west of the lime- 



