452 



THE AZOLC SYSTEM AND ITS SUBDIVISIONS. 



belonging to the Huroni.an.' I suspect that thej belong to the same scries. I 

 distinguish three crystalline gneissic series : I. Laurentian (not to fcpeak for 

 the present of the Labrador), 11. Huronian, III. Terranovan [Montalbun] ; 

 these being respectively in the United States, the rocks of the AdirondaclvS, 

 the Green Mountains and the White Mountains. I hope you will be able to 

 decide whether there is any want of conformity between II and III in your 

 region. I should mention that in Hastings Co., Ontario, the three series all 

 are represented, and tliat there is apparently a strati graphical break between 



each As regards series II, which was in 1862 declared by Macfar- 



lane to be the same with the Green Mt. group, I have for some time been 

 of that opinion, and have briefly expressed it in a paper on the rocks of 

 E. Mass., read last October to the Bost. Nat. Hist. Soc. (not yet published), 

 which compares the dioritic, chloritic and hornblendic rocks of the two 

 series. Their copper, nickel and iron ores are characters in common. My 

 opportunities for studying the Iluronian had been very imperfect, as Mr. 

 Murray's collections were so, and were made many years ago, and since re- 

 main, with few exceptions, packed away. It was not, therefore, till I saw the 

 Huronian rocks displayed along the coast of New Brunswick, that I realized 

 how much they were like the Green Mt. rocks, all of the types of which may 

 be found on the Bay of Fundy from Eastport to the head of the bay. ... . 

 I have thus, I think, touched on the principal points of interest in your collec- 

 tion, of which the two great facts are the close resemblance, and I believe the 

 identity, of the great iron-hearing dioritic-talcose series, with Green Mt. series 

 II, and the equally close resemblance of the rocks, 1215, 1151 to 1154, with the 

 White Mt. series III, which I conceive to belong to a higher horizon (see on 

 this a note to my paper on granitic rocks, 2d part, Am. Jour. Sci. for March)," 



While in the above letter it is written : "You say ' that they arc the 

 youngest rocks in the region belonging to the Iluronian.' I suspect 

 that they belong to the same scries," — in the " Azoic Kocks," it reads : 

 "You say that they are the youngest' rocks in the region belonging to the 

 Iluronian. I suspect that they belong to a younger series." {l. c, 

 p. 223.) 



Another letter by Dr. Hunt of the date of May 20, 1878 (Geology of 

 Wisconsin, III., 1879, p. 660), contains the following: 



" The announcements made in my letter to you identifying the fonuations 

 XIX and XX (the micaceous schists, with hornblendic and staurolitic schists 

 and the white feldspathic gneisses) with the Montalban, which I at that time 

 (1871) ventured to declare to belong to a newer and distinct series from the 

 Huronian, M'cre, as you know, an anticipation ^of some years of the published 

 conclusions of yours that they are the youngeat Iluronian racks, a strong con- 

 firmation of the great value of the distinctions, which in my Letter to you of 

 February 22, 1871, were presented /or the first time. All my subsequent work 

 in Pennsylvania (Proc. Amer. Assoc. 1876) and in North Carolina, as well aa 



