EVOLUTION OF IRONDEOUOIT VALLEY 



141 



northwest corner in the notch leading down the deep section beyond. 

 Thirteen range betAveen 19 and 28 feet but are either at the extreme 

 south end or else fall ujjon the marginal slopes. The average of the 

 remaining 104 is 38^^ feet. Just one-quarter of these (26) are imder 

 o5 feet, located mostly near the sotith end, while over a half ( 54) are 



"t^^fl^ 



"'^f'"' 



^rT,nfm. 



/ ex a^ffet-jticin X-^2. 



Fig. 3. Underwater Contours and Longitudinal Profile of Irondequoit Bay, 

 constructed from blueprint of U. S. Army map of 1875 and reduced to 

 one-sixth. The absence of meander cuts in the broad section (C-D) and 

 their abundance in the deep section (B) is strikingly brought out by the 

 contours, as also the narrow submerged wave-platform surrounding 

 the entire deep basin, showing how rapidly the silt bluffs are being eaten 

 back. 



either 39, 40 or 42 (41 feet being nowhere shown). This section 

 possesses therefore a remarkable flat floor, extending a mile and a 

 half north from the preceding section. 



Opposite the Newport House, however, the Bay deepens again 

 as suddenly as it narrows, and 127 soundings in this deep section 

 (B) show only nine under 42 feet all of which are distinctly mar- 

 ginal, while 91 are sixty feet or more, four being 81 feet and 

 one 84 feet. The remaining 27, ranging between 42 and 57 feet, 



