REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 r6T 



rock to another^ they nearly always show at least a rude banding, 

 at least two sorts of gneiss occurring in nearly every exposure, 

 sometimes in rapid alternation, sometimes in thicker bands. 

 The two commoner mixtures are of a red, granitic gneiss with a 

 hornblende gneiss, or of a somewhat different, red, acid gneiss 

 with gray, granulitic bands, usually of pyroxene granulite. In the 

 former case both rocke seem igneous and the granitic gneiss cuts 

 the other, but usually it has injected a multitude of thin sheet* 

 of granite along the foliation planes of the other rock, and the 

 whole has been drawn out so as to produce a distinctly banded 

 appearance. The other rocks are of uncertain origin and nature. 

 Other sorts of gneiss also occur. Such rocks occur in more or 

 lesis abundance all about the border of the Adirondack region, 

 as well as in patches in its heart. And the same, or at least 

 very similar rocks are found associated with, apparently often, 

 interbanded with, the limestones and clastic gneisses of series 2. 

 It would appear that, in so far as they may be clastic, they belong 

 to, and should be classed with, that series. In so far as they maj 

 be igneous, they seem in the majority of cases to be later than 

 the elastics, though intimately interwoven with them and much 

 earlier than the main eruptive series. If there are any rocks in 

 the region which are older than those of series 2, they are to be 

 found among these gneisses, but none have yet been definitely 

 shown to be older. But there is, as yet^ no evidence of any sort 

 concerning the age of much of this gneiss. In the writer's judg- 

 ment, a considerable part is to be classed with the Grenville rocks, 

 series 2, mainly consisting of closely contemporaneous igneous 

 rocks. It is by no means improbable that all should be so classed, 

 and that the Adirondack pre-Cambrian can all be placed under 

 Kemp's series 2 and 3. But, whether this be ultimately proven 

 to be the case or not, and if the expansion of series 3 here urged 

 be accepted, there will still remain a considerable body of gneiss 

 for which a separate subdivision is a convenience, if not a neces- 

 sity, in OTir present state of ignorance. The writer simply wishes 

 to urge the other point of view as a possible one, to be used as a 

 working hypothesis in further investigation in the region, and to 



