STATE GEOLOGIC MAP OF 1901 19 



copper plates would have been nearly as great as the expense 

 of the original engraving. It was, therefore, decided to use for 

 the new edition the less expensive method of photo-lithographic 

 reproduction and leave to a future period, when the topographic 

 survey of the state might be completed, the engraving of a new 

 copper plate base of which the accuracy might be unquestioned. 



The compilation of the manuscript geographic base was made 

 by draftsmen under the supervision of Mr C. C. Vermeule, on 

 the scale of 2J miles to the inch, using all atlas sheets that had 

 been surveyed at that time. In areas for which atlas sheets had 

 not yet appeared the most accurate county maps were followed. 

 The lithographic work was done by Julius Bien & Co., and after 

 the proofs of the base were submitted they were again revised 

 with the help of all later topographic sheets that appeared up 

 to the time of going to press. The compilation of the geology 

 was made with great care, preparation for it being the compila- 

 tion during the previous year of a manuscript map of the state 

 on a scale of 12 miles to the inch, in order to bring together 

 all the latest material and to form a definite idea of its adjust- 

 ment. Detailed credit for the material used is given in the text 

 of this bulletin and in the important work of adjustment the 

 writer has been greatly aided by his assistant Mr E. C. Eckel. 

 The drafting of the geologic boundaries on the new base was 

 mainly done by Mr A. M. Evans to- whose manual skill and geo- 

 graphic instinct much of the value of the map as an accurate 

 reproduction is due. 



It should be understood by those who use the map that a 

 certain percentage of the boundaries shown on it are necessarily 

 conjectural. Some, because they have not yet been carefully 

 surveyed on topographic sheets; some because the extent of 

 Quaternary deposits is so great as to render these boundaries, 

 in a large measure, indeterminate. One of the more prominent 

 examples of the latter class is the boundary between the Niagara 

 and Salina formations, west of the Genesee river. It can not 

 be promised that this boundary will ever be defined with any 

 degree of certainty unless a very extensive system of borings be 

 made. 



