158 ROCHESTER ACADEMY OF SCIENCE. 



banks are strongly leveed, until finally these levees push out into the 

 open waters of the Bay at its mouth in truly Mississippi fashion. 

 Beyond this the filling still continues northward just under water 

 for a mile to Glen Haven. 



A heavy bar at the north end of the Bay closes what would 

 otherwise be a splendid natural harbor. This bar has been built 

 from both ends, with sand from the west derived from the silt bluffs, 

 but from the east of rolled red sandstone pebbles from where the 

 surf is attacking the rocks beneath the bluff at Forest Lawn. Lake- 

 ward from this bar extends the broad subaqueous platform of' the 

 Genesee silts ; bayward of it the same or a similar shoaling reaches 

 far in, until it drops suddenly from 6 to 60 feet of water. The 

 long concavity of the main shore line on our map, and probably also 

 the minor concavity behind the bar, has been shaped by deej) and 

 prolonged wave erosion of the contorted silts along the ancient 

 delta margins, a process to which wind work contributes in no 

 small degree. 



Man's cuntrlhiitiun to the present stage. In the face of the 

 great operations here recorded man's efforts have been weak indeed. 

 He has reinforced the outer bar of the Bay with a railway embank- 

 ment built up especially at the two ends. He has cut a "ship canal" 

 (in the early days and long since abandoned) for small craft, 

 through the Irondequoit fioodplain swamps, to make Zarges Mills 

 (then Rich's Landing) his harbor. He has dipped in here and there 

 for gravel and sand, has graded his roads and built his bridges. But 

 neither white man nor aborigine has been more than a passive spec- 

 tator in the making of those topographic features by which we have 

 been unravelling the jiast. Yet the time is approaching when this 

 may no longer be true, — when with the growth of the city and the 

 accrescence of man's ingenuity many of the landmarks we have been 

 recording will be blotted from existence, the present forces har- 

 nessed to new tasks of man's own devising and the face of nature 

 stamped more indelibly with the brand of his artifice. It is time 

 therefore that these studies should be ])rinted before such changes 

 come about, both as a permanent record of the present phenomena 

 and their interpretation, and even more as an incentive to a larger 

 general interest in the acquisition and preservation of the further 



