ANCIENT WATER LEVELS OF CHAMPLAIN— HUDSON VALLEYS 67 



work began at the month of the Hudson and was carried north- 

 ward. At the beginning of the work in the Hudson valley the 

 contoured maps were relied on for obtaining the elevations of the 

 deltas and terrace deposits; later in the Champlain valley the use 

 of the aneroid barometer was availed of in checking data of the 

 same sort and for getting elevations where this mapping has not 

 yet been extended. More precise and satisfactory methods of 

 measurement would have more than doubled the length of time 

 which the work has taken. The field work was mainly done 

 during the summer seasons of the four years from 1900 to 1903 

 inclusive. 



After work in the Champlain valley had been begun by the 

 writer, Mr G. K. Gilbert of the United States Geological Survey, 

 who had previously made an examination of the country from 

 Lake Ontario around the northern slopes of the Adirondacks into 

 the Champlain valley as far south as West Chazy, generously 

 offered to the author through the state geologist the results of his 

 investigation. I have made the freest use of these notes both in 

 the search for localities and as a check on my conclusions, and 

 particularly have 1 been guided by Mr Gilbert's observations and 

 conclusions in regard to the fixation of the marine limit on the 

 northern side of Covey hill in Canada. The placing of the marine 

 limit from that point southward, however, is entirely on my own 

 responsibility and this distinguished geologist is in no way 

 involved in any mistakes which I may have made in my endeavor 

 to determine the extent, the elevation and the degree of tilting 

 of the ancient water levels described in this paper. In this report 

 no use has been made of the data from the northwestern slope of 

 the Adirondacks other than to include a record of the fossil shells 

 found near Norwood, N. Y. Special acknowledgments are due to 

 Dr F. J. H. Merrill, who has in many ways both in the field and 

 in the office contributed to the work of the author. I have also to 

 thank the officers of the Geological Survey of Canada for numer- 

 ous kindnesses in the granting of information and guidance, and 

 to Prof. A. P. Coleman for giving me the advantage of his greater 

 experience with ancient shore lines by personally visiting with me 

 some of the critical areas of northern New York. 



