Dale — Camhrian Conglomerate of B'qAon in Vermont. 269 



tlie larger pebbles of which measure 12 to 15 inches across. 

 No glacial striiB were made out on any of the pebbles. 



A number of pel)bles from these various localities M'ere 

 studied microscopically and fall into these groups: Blue quartz ; 

 biotite granite (medium -coarse) ; biotite-muscovite granite 

 (fine); biotite granite or biotitic quartz monzonite (fine) ; mus- 



FiG. 2. 



Fig. 2. Beach pebbles of pre-Cambrian gneiss and blue qiiartz weathered 

 out of Lower Cambrian metamorphosed conglomerate on the east spur of 

 Mount Moosalamoo, 1/2 mile E.N.E. of top, in Ripton, Vt. Sledge 30 inches 

 long. Largest pebble 23 x 16 x 7 inches (gneiss). 



covite granite ormuscovitic quartz monzonite (fine) ; museov^ite 

 granite-gneiss (fine) ; aplite-gneiss, pyritiferous (tine) ; quartz- 

 ite, two small pebbles from locality near Mount Moosalamoo.* 

 Both quartzite and igneous rock pebbles contain rhombs and 

 irregular plates of a ferruginous carbonate passing into limon- 

 ite, which are also characteristic of the pre-Cambrian gneisses 

 about Ripton. 



As to the origin of these pebbles : With the exception of the 

 quartzite and the aplite-gneiss all these rocks have already 

 been found in situ in the pre-Cambrian area shown in fig. 1. 

 The blue quartz is identical with that of a mass cut by the 



* Determination of aplite by E. S. Larsen, Jr., of U. S. Geol. Survey, 

 that of quartzite confirmed by him. 



