THE CAMPBELL BEACHES. 407 



BEACHES OF THE CAMPBELL, STAGES. 



The Campbell shore-lines have in general somewhat the most conspic- 

 uous development of all below the Herman series. They belong to stages 

 of Lake Agassiz much below its highest level, and furnish a very useful 

 record of the boundary and depth of this body of water, as shown on 

 PI. XXXIV, near the time wlien it ceased to outflow to the south at Lake 

 Traverse. Considerable portions of the lower and principal Campbell 

 shore are marked b}^ a low, eroded escarpment in the general sheet of till; 

 and the aggregate length of such terracing by this one level of the lake is 

 probably equal to that of the numerous shorter lines of escarpment formed 

 during all its other levels, both above and below. Probably the laud 

 reposed without ujjward movement longer at this stage than at any other 

 in the history of the lake, unless the earliest and highest stage of the Her- 

 man series must be excepted. It is also to be remarked that no other shore 

 of Lake Agassiz bears at any place so extensive an embankment of beach 

 gravel and sand, transported a long distance by the action of waves and 

 coastal currents, as that swept southward from the Pembina delta during 

 the Campbell stages. 



Between the rate of northward ascent of the uppermost Herman beach 

 and that of the Campbell beach there is a remarkable contrast. Along the 

 300 miles from the mouth of Lake Agassiz to Gladstone explored by me 

 the land had been considerably uplifted after the formation of the Herman 

 beach; but its level in all this extent has been only slightly changed since 

 the old lake shore was at the present site of the town of Campbell, in Min- 

 nesota. Farther to the north, however, on the east side of Duck Mountain, 

 a large amount of diff'erential northward uplifting took place after the 

 Campbell stages of the lake. The rate per mile of northward ascent of 

 the Campbell beaches there exceeds that of the first and highest Herman 

 beach upon all the country south of Gladstone. 



Unusual interest, therefore, appertains to the Campbell shoi-es, and they 

 have been more fully mapped, especially in North Dakota, with leveling to 

 ascertain their height continuously, than anj^ other of the successive lioun- 

 daries of this glacial lake, whether belonging to its stages of southward or 

 of northeastward outflow, excepting only the Herman beaches. 



