REPORT 
OF THE 
SURVEY OF THE FOURTH GEOLOGICAL DISTRICT. 
CHAPTER I. 
PRELIMINARY CONSIDERATIONS. 
The Fourth District comprises fifteen and a half counties, as previously enumerated ; and 
embraces all that part of the State lying west of the parallel of Cayuga lake, and included 
between the Pennsylvania line on the south and Lake Ontario on the north. 
The succession of strata, occupying the different portions of this district, have been made 
known from time to time, in the several Annual Reports presented to the Legislature. It 
now remains to give a connected view of these, with their striking features and fossil contents ; 
the object of the work being to aid those who wish to obtain a knowledge of our rocks, and 
also to show as far as possible, by an exhibition of their distinctive features, the reasons on 
which the subdivisions have been founded. With this design, some wood-cut illustrations are 
given of characteristic scenery, when the rocky strata are exhibited. The principal illustra¬ 
tions, however, are those on which the geologist depends when making his explorations in 
the field — the organic contents of the rock. Wood-cuts of the most important and charac¬ 
teristic fossils of each rock and group are inserted in the text, under the proper heads. Thus 
each rock will be represented in its most characteristic fossils, which will greatly aid the stu¬ 
dent who has not the advantage of an arranged collection for reference, and enable him to 
decide from a few specimens the situation of the mass he is examining. This mode was 
adopted, believing it would be impossible to present a satisfactory report without such illus¬ 
trations. 
Geol. 4th Dist. 
1 
