GEOLOGICAL MAP. 
681 
PLATE XVI. 
Ravine at Hammondsport, Steuben county. Rocks of the Portage group. This is a common feature 
in the scenery of the southern counties. 
PLATE XVIL 
Hector falls, Tompkins county. This waterfall is almost directly from the top of the cliff into the lake, 
the gorge being worn back but a very short distance. Rocks of the Portage group. 
PLATE XVIII. 
Lodi falls, Seneca county * This fall of water is over the rocks of the lower part of the Portage group, 
at the head of a gorge three-fourths of a mile from Seneca lake. 
PLATE XIX. 
Deep gorge of the Genesee below the Middle falls at Portage. The cliffs below the falls are of the 
rocks of the Portage group, three hundred and fifty feet in perpendicular height. 
GEOLOGICAL MAP OF THE MIDDLE AND WESTERN STATES. 
In this map are laid down the limits of the principal geological formations occupying the States of 
New-York, New-Jersey, Pennsylvania, Delaware, Maryland, Virginia, Kentucky, Ohio, Indiana, 
Michigan, Illinois, and a part of Wiskonsan and Missouri. A portion of Canada, bordering the great 
lakes, is also added. The accompanying table of colors, and the sections 3 and 4, plate xm, will give a 
correct idea of the order of succession among the principal strata. 
Note. The first intention in constructing this map, was to show the extent of some of the New-York formations be¬ 
yond the limits of the Fourth District in a westerly direction. As the work progressed, new materials accumulated, 
and a tour over the western States offered an opportunity of presenting the unbroken continuation of many of the New- 
York rocks as far as the Mississippi river. 
In laying down the formations upon this map, the annual reports of the different States furnished valuable data; and 
although I had travelled over the country in different directions between the Atlantic and the Mississippi, and was well 
acquainted with its general features and the outlines of the more important groups, still I should have been unable to 
give the exact limits of many of these formations but for the kind assistance afforded by many of my fellow laborers; 
thanks to the enlightened and liberal spirit, which in the free communication and interchange of information has so 
rapidly advanced our knowledge of American Geology: and it is with pleasure that I acknowledge my obligations to the 
By an error of the engraver, the plate is printed “Lodi falls, Genesee county/ 
