Cushing — Igneous Rocks of the Adirondack Region. 289 



as belonging to a single vast intrusive body. Evidences for 

 this view are presented below."* 



Early in his paper Miller thus states his view. Search in 

 the body of the paper for these promised evidences shows 

 them to be : 



(1) A table of chemical analyses, comprising eight analyses of 

 syenite and three of granite, introduced to show their similarity 

 in chemical composition. Nine of the eleven analyses were 

 made by Prof. Morley, seven of them for me and two for Dr. 

 Miller. Of the three granites one is a granite-porphyry 

 variant of the syenite, and the other two are of rocks from the 

 Thousand Island region, for which I have suggested a 

 Laurentian age. The similarity of the rocks as shown by the 

 analyses is not questioned. Whether kinship in age may be 

 legitimately deduced from chemical similarity is quite another 

 matter. 



(2) A description of the known variations of the syenite 

 magma, including its granitic phases. Since we have all 

 recognized and described such variations, this calls for no 

 comment except to point out that the presence of granite of 

 such age and relationship has nothing whatever to do with the 

 possibility of there being another of quite different age also 

 present. And if there be more than one there is every 

 reason why they should be akin chemically, since they probably 

 have arisen from the same deep-seated source, and through the 

 same rocks. 



' (3) In Dr. Miller's Adirondack experience he has in no case 

 been able to find any evidence that any of the Adirondack 

 granites are distinctly older than the syenite, while he has 

 many times found that granites are only siliceous variations or 

 phases of the normal syenite. He states that, in the Adiron- 

 dacks, no definite case of syenite cutting granite has been found, 

 and but one good case of granite cutting syenite. He seems 

 to regard this lack as of special significance in support of his 

 contention. He also argues that if such evidence were forth- 

 coming it would not disprove his contention, since all igneous 

 masses, when cooling, become cut by dikes of their own 

 material. 



It is because, in my Adirondack experience, I have found 

 plenty of what to me seems very good evidence that there 

 were at least two widely separated periods of granite intrusion 

 in the region, that this paper is being written. In many times 

 finding granites that are variants of the syenites, and describing 

 them, my experience is on all-fours with Dr Miller's. But I 

 have been more fortunate than he in making the acquaintance 

 of other granites. He assumes all the syenite to be of the 



*Op. cit., p. 244. 



