January 24, 1919J 



SCIENCE 



79 



schist besides the eroded limestone ought to be re- 

 stored to the valley (and) where the Cambrian 

 limestone comes to the surface in anticlines, the 

 entire limestone formation as well as the schist 

 ought to be added, i. e., at least 3,500 and possibly 

 5,000 feet, leaving out the Silurian Grit. 



The differences in form are clear when the 

 two ranges of mountains are before one, but 

 they are not easily described. The Green 

 Mounfains are characterized by rounded, 

 though not dome-shai)ed, summits, frequent 

 long ridges radiating from them and occasion- 

 ally sharp cliffs, but nowhere is there the very 

 rugged, angular, pyramidal outline of the 

 Matterhom type. 



The greater part of the mountain mass con- 

 sists of gneiss and, of course, the general 

 forms of the various summits are due to the 

 effect of long weathering and glaeiation upon 

 this material. 



The outlines in the Taconics are even more 

 rovmded than are the Green Mountains, the 

 mass is often more elaborately dissected, the 

 ridges more numerous and longer. Beginning 

 in Snake Mountain in Addison, somewhat 

 north of the middle of the state is a series of 

 low mountains and hills, nowhere imited in a 

 range, but standing as isolated elevations not 

 far from the shore of Lake Champlain. 



Xearly all of these are less than a thou- 

 sand feet high, though one or two are more, 

 and they are mostly composed of Lower Cam- 

 brian red sandstone, but there are occasionally 

 shale and quartzite. Silicious limestone of 

 the same age also occurs in small amount. 

 This series has been known as The Red Sand- 

 rock Formation, but as this name is preoccu- 

 pied and as the terrane as foimd in western 

 Vermont appears to be sufficiently distinct to 

 desen-e a local name, it is suggested that these 

 beds of sandstone with some shale, quartzite 

 and limestone be called the " Winooski Beds." 



Among the characteristic fossils are Olenel- 

 lus thompsoni, Ptychoparia adamsi, Kutorgina 

 cingulate, BillingseUa orientalis, Huenella ver- 

 montana. These place the terrane in the 

 Waucobian of Walcott. 



It seems evident that the outcrops in the 

 lowlands and in the elevations — the series of 



hills — are Cambrian remnants and that before 

 the Ordovician, Cambrian strata some thou- 

 sands of feet thick covered the western part 

 of Vennont. 



What has been called " The Champlain-St. 

 Lawrence Fault" came after the close of the 

 Ordovician running from Canada through 

 western Vermont and on along eastern New 

 York. This broke through the Cambrian and 

 Ordovician, lifted the eastern side hundreds 

 of feet above the western and shoved it over 

 so that now in many places on the shore of 

 Lake Champlain beds of Lower Cambrian rest 

 directly on those of the Utica Shale, which is 

 at the water's edge. These exposures are very 

 impressive as they form cliffs on the shore of 

 the lake. 



The foiu-th series of elevations in Vermont 

 are not very numerous nor massive, but com- 

 mercially they are of great importance be- 

 cause it is in these Granite Hills that all the 

 granite quarries are situated and Vermont at 

 present leads the world in production of this 

 stone, as it does in marble. 



As the Taconics and Cambrian Hills are 

 west of the Green Mountains, so these are on 

 the eastern side — a series of low momitains 

 wholly of granite, usually more or less dome- 

 shaped and not more than a few hundreds of 

 feet high. Millstone Hill in Barre and Robe- 

 son Moimtain in Woodbury are types of these 

 granite masses. Probably all are laccoliths 

 and as the granite has a structure that indi- 

 cates slow cooling of intrusive masses held 

 down by heavy pressure, there was originally 

 a considerable thickness of other rock resting 

 upon the upthrust granite. 



As Ordovician fossils have been found in 

 the unchanged limestone near the granite, it 

 seems probable that the covering beds were 

 of this age, though there may be some of the 

 Cambrian as well. 



The rocks now associated with the granite 

 are metamorphic so that the igneous activity 

 which resulted in the granite thrust did not 

 take place until after the great metamorphism 

 following the Ordovician. It has been thought 

 that it did not occur till the Devonian or even 

 somewhat later. 



