1892.] NEW YORK ACADEMY OF SCIENCES. 21 



It is a curious fact that the porphyry and trap classed with 

 the primary are described as penetrating the Utica slate, and 

 that sienite of the Statilied division is also said to occur in 

 dikes. After a chapter on the ill-starred Taconic system, the 

 counties are taken up in order and described. In discussing 

 the primary system, Emmons says little of the respective ages 

 of the subdivisions, but he saw clearly the contrast of the 

 "granite" {i. e., the labradorite-hypersthene rocks) and the 

 gneiss. It must be remembered that he worked in a wilder- 

 ness and, considering his opportunities, he deserves the highest 

 praise. He writes with extraordinary abilit}^ and clearness, 

 and though, for instance, we have no confidence to-day in the 

 igneous character of his limestones, we must realize that con- 

 ceptions and knowledge of metamorphism have greatly 

 advanced since his time. 



The dearth of papers in the next thirty or forty years is 

 remarkable. The Canadians had country of much the same 

 character to deal with, and the problem of the subdivision of 

 the old crystalline rocks was attacked by them. The Adiron- 

 dacks are often referred to, but no detailed field-work was done 

 in them. The relations of the gneisses, the norites or anor- 

 thosites and the crystalline limestones have been and^are the 

 problems meriting attention. As is well known the gneisses 

 were generally called Lower Laurentian, and the norites. Upper. 



A number of papers remain to be noted, which treat of 

 restricted parts of the subject. The late Dr. T. S. Hunt 

 published in 1871, a valuable contribution on the Mineralogy of 

 the Laurentian limestones (21st Annual Report N. Y. State 

 Cabinet, p. 47, 1871), but has comparatively little to say of their 

 geognostic relations. James Hall presented to the American 

 Association at the Buffalo meeting, 1876, a paper on the Age 

 of the Serpentinous Limestones of Northern N. Y. It was 

 published in the Biift'alo Courier, Aug, 25th, and from this was 

 abstracted for the American Journal of Science of October of 

 the same year. Professor Hall regarded the limestones as later 

 than the Laurentian and earlier than the Potsdam, but whether 

 Huronian or not he does not say. The paper is rather general 

 in character and gives no actual sections or data of localized 

 character, at least in the printed abstract. 



In 1877 Dr. Albert R. Leeds published a paper entitled 

 " Notes on the Lithology of the Adirondacks '' (Chemical 

 News, Mar., 1877; 36th Ann. Rep. N. Y. State Cabinet, 1877, p. 

 79). Dr. Leeds' material came mostly from tke Keene Valley 

 and consisted of varieties of norite and of several diabase dikes. 

 Very careful chemical analyses are given, and some microscopic 



