142 ROCHESTER ACADEMY OF SCIENCE. 



are restricted to two very definite small platforms on mid-west and 

 northeast, perhaps contemporaneous in origin with the ])receding' 

 flat-bottomed section. The form of the under-water contours in 

 this section B is that distinctive of a gorge-like valley widened 

 slightly by meander sweep, contrasting strongly with the absence 

 of any such meander-cuspings in the preceding sections C and D. 



The maximum depth of 84 feet anywhere in the Bay is in this 

 narrow section and about opposite Point Pleasant. With the widen- 

 ing of the Bay towards its mouth the soundings jump abruptly from 

 60 feet up to barely six ( one fathom ). 109 soundings in this shallow 

 northerly section (A) include only eleven over six feet all of which 

 are in the northeast corner farthest from the inlet. Over half (52) 

 of the remaining 98 are either 3 or 4 feet, and these are distributed 

 on the western half which thus constitutes a typical inlet delta. 



The longitudinal profile of the Bay. as shown in Figure 3. 

 therefore contains four sharply distinguished segments. — three of 

 them (A, C, D) approximately flat platforms and the fourth (B) a 

 gorge-like trench. The principal platform is in the middle and wid- 

 est portion of the Bay, with an average depth of about 40 feet but 

 declining cjuite steadily though gently from south to north. The 

 other two flats are the shoal i)ortions at each end of the Bay. In 

 the very deep, gorge-like segment the depths increase pretty steadily 

 from the Newport House to Point Pleasant, and thence shallow 

 again about one fathom. Each of these four sections is separated 

 from the adjoining ones by abruj)t vertical transitions of 25 to 50 

 feet. In attempting to interpret their testimony it is obvious that 

 the shoals at either end are the work of the present waterplane, but 

 the broad flat bottom of the middle bay and the deej) channel through 

 tlie narrow section originated in ei)isodes when the waters in the 

 Ontario Basin stood much lower than to-day. Our conception of 

 their meaning is recited on a later page, in the paragraphs on the 

 re-excavation of the valley. 



Course and character of the "dugzcay" valley. The erosional 

 forms assumed by the silts in the "dugway"' portion of the valley 

 look at first sight exceedingly complicated, but on more minute 

 analysis their peculiarities and irregularities are found to be highly 

 instructive. At Zarges Mills the present course of the river bends 



