TRANSACTIONS OF SECTION C. 729 



the other localities. He saw no relation whatever hetween the typical Huronians 

 and the British ' Pebidian,' and other rocks which had been compared to them, 

 though the latter had some resemblance to the ' Animike ' group of Port Arthur. 

 He drew special attention to the volcanic nature of a great part of the Hastings 

 series, and compared these with the so-called ' Arvonian ' portion of the Pre-Cam- 

 brian of Great Britain. 



G. On the Southward Ending of a great Synclinal in the Taconic Range. 1 

 By Professor James D. Dana, LL.D. 



The Taconic Range, which gave the term 'Taconic ' to geology, lies in "Western 

 New England, between Middlebury, in Vermont, on the north, and Salisbury, in 

 Connecticut, on the south. In former papers, published in the ' American Journal 

 of Science,' the author has shown, first, that the rocks constituting the range vary 

 as we go from north to south, from roofing-slate and hydromica (or sencite) 

 schist to true chloritic and garnetiferous mica schists ; secondly, that these schists 

 lie mostly in a synclinal or compound synclinal ; thirdly, that the crystalline 

 limestone along the eastern foot is one with that along the western, the limestone 

 passing under the schist as a lower member of the synclinal; and, fourthly, thar, 

 since the limestone contains in Vermont (according to the discoveries of the 

 Vermont Geological Survey, and also of Mr. A. Wing), and in the State of New 

 York, fossils of the Lower Silurian, ranging from the inferior divisions to the 

 higher, the Taconic schists are probably of the age of the Hudson River group or 

 Llandeilo flags. . 



The author's papers further show that while a large part of the Taconic Range 

 has an eastward dip on both the east and west sides, a southern portion about 

 twelve miles long, consisting of Mount Washington in south-western Massachusetts 

 and its continuation into Salisbury, Connecticut, is a broad tray-shaped synclinal, 

 the dips of the two sides being toward one another, like the sides of an ordinary 

 trough. The width of the broad synclinal between the limestone belt on either 

 side is about five miles. 



As the result of investigation during the last two years, the synclinal character 

 of this Mount Washington part of the Taconic Range'is illustrated in the paper by 

 new sections, and by facts connected with the dying out of the great synclinal (or 

 compound synclinal) in the town of Salisbury. 



The mean height of Mount Washington above the sea-level is about 2,000 feet, 

 and above the wide limestone region on either side and to the south, about 1,250 

 feet. The synclinal virtually ends along an east and west line through the village 

 of Lakeville, in the town of Salisbury, where a beautiful lake lies within 

 the limestone area. The surface of the mountain region descends 1,000 feet in the 

 southern, or last, three miles ; and in the latitude of Lakeville the width, as the 

 map presented shows, diminishes abruptly from five miles to a narrow neck of six- 

 tenths of a mile. The area south is of limestone, and the neck of schists referred 

 to is hardly 150 feet in height above it. 



The limestone may in some places be seen emerging from beneath the schist at 

 a small angle ; and at one locality a low oven-shaped anticlinal of limestone has 

 the schist covering all but a narrow portion at top ; the quarrymen had to remove 

 the schist to work at the limestone. Several narrow strips or belts of limestone, 

 S. 15° W. in direction, corresponding with the direction of this part of the range, 

 show out through the sides of the mountain where local anticlinals have had their 

 tops worn off. Further, the dip of the schist over much of the southern slope is 

 southerly and at a small angle, but with many local anticlinals and synclinals. In 

 addition, there are small areas of schist in the limestone region, like straggling por- 

 tions of the dwindled mountain, which appear in general to be remains of local 

 flexures. 



There is the plainest evidence that the limestone formation of southern and 



1 Printed in full in American Journal of Science, Ser. 3, vol. xxviii. pp. 268-275, 

 with map and six woodcuts ; 1884. 



