GENERAL TOPOGRAPHY 327 



We hope year by year to add the geology of new townships to those 

 already mapped, until the whole region has been carefully covered. 

 The problems are not easy ones and the many questions require very 

 thorough exploration. 



The present contribution is only concerned with Moriah and 

 Westport townships. The Held work was done in the summer of 

 1892, but the writer has been making excursions into the mountains 

 for five years past, and a general introduction is given, based on the 

 data thus gathered. 



In the field work efficient assistance was rendered by Mr W. D. 

 Matthew, late Fellow in Geology, Columbia college, and acknowl- 

 edgments for indispensable aid are here gladly given. 



GENERAL TOPOGRAPHY AND GEOLOGY 



The country along the western shores of Lake Champlain, is 

 diversified in its contours. While the larger share of the water- 

 front is formed of the later sedimentary strata, and while these do 

 not reach in the townships here described, a height of much over 

 400 feet above the lake (this is not far from 500 feet above tide) 

 they are either soon succeeded in the region south of Plattsburg, by 

 the gneisses, serpentinous limestones, gabbros and anorthosites* as 

 one goes inland, or else are cut by spurs of the latter which jut out 

 in high ridges to the water itself. The heart of the Adirondacks is 

 formed of the anorthosites and the highest peaks are dome-shaped 

 masses of this rock. But the flanks on all sides consist largely of 

 qnartzose gneisses, and more or less of serpentinous limestones, which 

 latter have interbedded with them black hornblendic and pyroxenic 

 schists, and are heavily charged with bunches of silicates. The 

 gneisses attain to less altitudes than the anorthosites, although in 



* The term anorthosite has been long in use among Canadian geologists, as a 

 special name for the rocks of the Norian series, that consist almost entirely of 

 plagioclase. It is derived from the old French word "anorthose," which is a 

 collective term for the triclinic feldspars. While with New York geologists. 

 norite is generally used for the labradorite rocks, yet increasing observation shows 

 that true norites (i. e. containing plagioclase and orthorhombic pyroxene) are not 

 so general as at first supposed, and as gabbro is a much wider term, embracing 

 under it collectively, the gabbros proper, (plagioclase and monoclinic pyroxene), 

 the norites and the anorthosites, it is here employed. 



