REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 r9 



The Grenville series was seen to consist of rocks in every way 

 like those comprising the crystalline limestone series of the 

 Adirondacks. It seems also quite certain that the two series 

 may be directly followed from one district to the other through 

 the Thousand Island region, and it would appear quite proper that 

 the same name should be applied to the series in both districts. 

 It was also made apparent that the great mass of the gneisses 

 of the x^dirondacks would be classed with the Ottawa gneiss by 

 the Canadian geologists, were the Adirondack region a part of 

 Canada. But, on the other hand, it was manifest that other rooks 

 were also included here which do not appear in the Adirondacks 

 at all, and the propriety of using this name in the Adirondacks is 

 perhaps not so evident as in the case of the Grenville rocks. 



Field work in the Adirondacks was sadly hindered by the 

 almost incessant rainfall during July and August. The work 

 was confined to the vicinity of Tupper lake, its purpose being to 

 determine the limit of the Tupper lake augite syenite on the 

 west, and to determine, if possible, the relations of the syenite 

 to the anorthosite on the one hand, and to the surrounding 

 gneisses on the other. These relations are exceedingly obscure 

 and puzzling, and exposures which would aid in deciphering 

 them were not forthcoming. At one locality unmistakable 

 anorthosite was found, cut by what was taken to be augite 

 syenite. The intrusive is not typical and can not be traced 

 to connection with any body of syenite, yet is still regarded 

 as being of that rock. The syenite was found to run well 

 to the west in St Lawrence county, and is well exposed in the 

 many cuts along the New York Central and Hudson River 

 railroad between Tupper lake and Horseshoe. Except on the 

 east, where it is in contact with anorthosite, the syenite is sur- 

 rounded by a belt of granitic gneiss and amphibolite, and the two 

 are so blended and intermingled that no sharp boundary can be 

 drawn between them. Moreover, patches of the one are found in 

 the other, and vice versa. The relations are such that the two 

 would naturally be classed together as parts of the same great 

 series of gneisses. The workers in the Adirondacks have found 



