MEMORIAL OF H. J'. CUSHING 49 



By close observation in the field, checked by the help of the paleon- 

 tologists, Euedemann and Ulrich, and by the interpretation of the strata 

 in oscillations of the foundation rocks, a more detailed and correct classi- 

 fication was attained for the Cambrian and Ordovician beds around the 

 Adirondack Precambrian. 



In 1907 Professor Cushing was one of the three representatives of the 

 United States (C. E. Van Hise and J. F. Kemp being the other two) 

 who joined with the three Canadian geologists (F. D. Adams, A. E. 

 Barlow, and A. P. Coleman) in spending a month in the Adirondacks 

 and in eastern Ontario, in preparation for a report on the correlation and 

 nomenclature of the Precambrian formations on both sides of the national 

 boundary. 



In the succeeding years Professor Cushing began his studies in the 

 northwestern corner of the Adirondack area of ancient crystalline rocks 

 in the region of the Thousand Islands. In association with C. H. Smyth, 

 the Precambrian formations were mapped and interpreted, while E. 

 Euedemann aided in connection with the faunas of the Paleozoic and 

 H. L. Fairchild was busied with the Pleistocene. The resulting bulletin 

 of the State Museum dealt with five quadrangles and brought out many 

 important details. One of the first results was described in the first title 

 for 1910. In it Professor Cushing was able to show that a granite nor- 

 mally red bleached out to white where it lay next to invaded Grenville 

 limestone, some peculiar effect having been exercised on the color by the 

 limestone. A second result was the establishment of intrusive granites of 

 at least two ages. The older, called the Laurentian in conformity with 

 Lake Superior usage, is post-Grenville, but is foliated parallel with the 

 Grenville structures. The Laurentian granite was followed by the Alex- 

 andria syenite, presumably a northeastern extension of the syenite series 

 of the Adirondack Mountains. One minor exposure of gabbro was also 

 found. Certainly later than both Laurentian granite and Alexandria 

 syenite is the Picton granite, which has abundant inclusions of both these 

 older intrusions and also of the Grenville. Finally the usual diabase 

 dikes close the Precambrian, or at least precede the Potsdam sandstone. 

 Professor Cushing drew some interesting comparisons with the ancient 

 crystallines to the east and remarked the increasing metamorphism as 

 one goes eastward. The chapters on the early Paleozoic strata are also 

 of great importance, and interesting correlations are tabulated and dis- 

 cussed with reference to the Trenton Falls, Mohawk Valley, Saratoga, 

 and Champlain Valley regions. 



Professor Cushing, in association with Dr. Eudolph Euedemann, next 

 took up the mapping of the Saratoga Springs area, since agitation to 



IV— Bull. Geol. Soc. Am., Vol. 33, 1021 



