GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 9/ 



and the Quebec group." To this publication I have already made abun- 

 dant references in Volume I, page 522. 



In 1 87 1, in the presidential address before the American Association 

 for the Advancement of Science, Dr. Hunt thus defines the White Moun- 

 tain series: 



This series is characterized by the predominance of well defined mica-schists inter- 

 stratified with micaceous gneisses. These latter are ordinarily light colored from the 

 presence of white feldspar, and, though generally fine in texture, are sometimes coarse- 

 grained and porphyritic. They are less strong and coherent than the gneisses of the 

 Laurentian, and pass, through the predominance of mica, into mica-schists, which are 

 themselves more or less tender and friable, and present every variety, from a coarse 

 gneiss-like aggregate down to a fine-grained schist, which passes into argillite. The 

 micaceous schists of this series are generally much richer in mica than those of the 

 preceding series, and often contain a large proportion of well defined crystalline tables 

 belonging to the species muscovite. The cleavage of these micaceous schists is gen- 

 erally, if not always, coincident with the bedding, but the plates of mica in the coarser- 

 grained varieties are often arranged at various angles to the cleavage and bedding-plane, 

 showing that they were developed after sedimentation, by crystallization in the mass ; 

 a circumstance which distinguishes them from rocks derived from the ruins of these, 

 which are met with in more recent series. The White Mountain rocks also include 

 beds of micaceous quartzite. The basic silicates in this series are represented chiefly 

 by dark colored gneisses and schists, in which hornblende takes the place of mica. 

 These pass occasionally into beds of dark hornblende-rock, sometimes holding garnets. 

 Beds of crystalline limestone occasionally occur in the schists of the White Mountain 

 series, and are sometimes accompanied by pyroxene, garnet, idocrase, sphene, and 

 graphite, as in the corresponding I'ocks of the Laurentian, which this series, in its 

 more gneissic portions, closely resembles, though apparently distinct geognostically. 

 The limestones are intimately associated with the highly micaceous schists containing 

 staurolite, andalusite, cyanite, and garnet. These schists are sometimes highly plum- 

 baginous, as seen in the graphitic mica-schist holding garnets in Nelson, New Hamp- 

 shire, and that associated with cyanite in Cornwall, Conn. To this third series of 

 crystalline schists belong the concretionary granitic veins abounding in beryl, tourma- 

 line and lepidolite, and occasionally containing tinstone and columbite. Granitic veins 

 in the Laurentian gneisses frequently contain tourmaline, but have not, so far as yet 

 known, yielded the other mineral species just mentioned.* 



********** 



Although I have in common with most other American geologists, maintained that 

 the crystalline rocks of the Green Mountain and White Mountain series are altered 

 paleozoic sediments, I find, on a careful examination of the evidence, no satisfactory 



* Hunt, Notes on Granitic Rocks; Arner. your. Set., Ill, i, 182. 



