478 T. C. CHAMBERLIN — Till: [NTEBGLACIAL [NTERVAL. 



discovery with reference to these dep isits which connects those of the valley 

 of the Ohio with those of the Monongahela valley. Any of you who travel 

 along the Parkersburg branch of the Baltimore and < >hio railway will observe 

 that west of Clarksburg the railway crosses a summit. On one Bide the 

 water drains into the Oh in. and on the other into the Monongahela. It is a 

 broad, level Bummit, having an elevation of 1 ,100 feet, in a gap of probably 

 300 feel below the enclosing hills. Thai gap, or valley, is covered by a 

 deposit of fine clay. The cut through it is about 30 feet : and one can observe 

 the succession of clays of all kind- ami of different colors, from yellow on the 

 Burface down to the finest white potter's clay at the level of the railway 

 where the cut reaches bed-rock, thus proving that the region has been Bub- 

 merged. This submergence would carry a water-level up the Allegheny 

 valley into the region to which President Chamberlin refers, ami would 

 satisfactorily explain the phenomena there without recourse to a "second 

 glacial epoch," where the evidence of neither a " first " nor a " second " ever 

 existed. 



President Chamberlin: It. is the work of the geologist to distinguish 

 between the deposits formed by water running on a slope and those formed 

 by static or horizontal waters. These differences are char and sharp when 

 the formation- are well developed, and are capable of p isitive discrimination. 

 [n respect to the deposits on the Allegheny and Monongahela and upper 

 Ohio, to which reference has been made, I may say that several years ago 

 Mr. Gilbert and myself spent more than twenty days on this especial problem 

 of discrimination, and satisfied ourselves completely that they were formed 

 l>y running water, as I think Mr. Gilbert will say if an opportunity is 

 afforded. Mr. McG se has made similar observations on the deposits of the 

 upper Delaware and Susquehanna, and so has Professor Salisbury : and I 

 may say the same in reference to my own convictions regarding these river-. 

 In the case of the Allegheny and the Monongahela, taken together, the 

 facts are sharp and well defined, and 1 may make that case typical in my 

 answer. These terraces on the Allegheny and Monongahela rivers arc not 

 distributed in horizontal lines along the -lopes of the valley as if they were 

 formed by the stationary water by means of wave action on the valley Bide. 

 ~ oh wave action should be nearly uniform throughout the whole length, 

 •pi as long stretches or coincidence with the direction of the prevailing 

 wind- gave greater fore.'. There are certain characteristic inequalities in the 

 cutting of terraces by a body of stationary water, hut the laws and the 

 characteristics are well known, having been very beautifully and Bharply 

 brought out by those who have investigated the deposits of the western region. 

 On the other hand, the work done by streams is radically different. The 

 cm- wherever in it- meanderings it strikes with greater force, and 

 leaves such portions as happen to lie in its concave curves. The resulting 



