THIRD REPORT OF THE DIRECTOR I9Q6 II 



Valcour island, Lake Champlain. It has been the purpose to make 

 the study of this interesting isolated area more than a discrimina- 

 tion of its rock formations. Valcour island is a spot of singular 

 attractiveness for its location and salubrity; it is equally inviting 

 for the development and accessibility of its Lower Siluric rocks and 

 fossils. The survey of this island is being carried out on a much 

 larger scale than the uniform topographic maps, the contours being 

 drawn at i foot intervals. These investigations have led to in- 

 teresting paleontological discoveries which have furnished the basis 

 of two papers by Mr Hudson already published in the Museum 

 bulletins. 



Highlands of the Hudson. Dr C. P. Berkey reports the 

 completion of the areal survey of the crystalline rocks in the Tarry- 

 town sheet and the extension of his investigations to the West Point 

 sheet adjoining at the north. The region about Peekskill on the 

 southern margin of the Highlands has proved so complicated struc- 

 turally and • so incompletely differentiated stratigraphically that it 

 was found advisable to defer the continuation of the mapping until 

 these problems could be solved. With this purpose in view the 

 whole breadth of the Highlands has been examined, especially 

 regions of critical importance close to the Hudson river. 



The following statements summarize the best established con- 

 clusions from the investigations : 



1 The oldest formation of the Highlands is a gneiss, provisionally 

 designated the Highland gneiss and probably equivalent to the 

 Fordham gneiss of the New York city district. 



2 This gneiss is essentially a series of metamorphosed ancient 

 sediments chiefly silicious, now appearing as granite gneisses, 

 quartzite schists, mica schists with occasional interbedded limestones 

 and serpentinous beds. The whole series is abundantly interjected 

 with sheets, stringers and dikes of igneous origin of many varieties 

 and different dates. The most abundant types are granites and 

 pegmatitic granites which are occasionally intruded in such large 

 bodies as to form some of the most prominent ridges or mountains 

 of the region. Such masses are Storm King and Breakneck Ridge. 

 The older igneous intrusions are themselves sheared and recrys- 

 tallized into gneissic structure. 



3 At some places the gneiss-schist passes conformably and gradu- 

 ally into a quartz-schist and even into a quartzite of no great thick- 

 ness. This in turn is followed by a coarsely crystalline limestone of 

 several hundred feet thickness and, allowing for its greater mobility 



