﻿430 W. JV'. Rice — Trap and Sandstone in the 



Art. XLIX. — On the Trap and Sandstone in the Qorgp. of the 

 Farming ton River at Tariffuille, Conn.; by William North 

 ElCE. 



The trap of the Connecticut Valley, as is generally known, 

 occurs for the most part in sheets intercalated among the sand- 

 stones and associated rocks, and apparently perfectly conforma- 

 ble with the sedimentary rocks in their generally easterly dip. 

 Diverse views have been maintained in regard to the history of 

 these sheets of trap, some writers considering them contempo- 

 raneous, others considering them intrusive, and still others 

 holding that some of the sheets are contemporaneous and others 

 are intrusive. The last view is set forth by Prof. W. M. Da- 

 vis, in his paper " On the Relations of the Triassic Traps and 

 Sandstones of the Eastern United States,"* a paper which, in 

 addition to most important original observations bearing upon 

 the question, gives a very complete resume of the literature of 

 the subject. If it be true, as I believe it is, that some of the 

 sheets are contemporaneous and others intrusive, there is ob- 

 viously need of special study to make out the history of each 

 one. My purpose in the present note is to offer a contribution 

 to this study by calling attention to one remarkably instructive 

 locality. 



The long range of trap hills which extends almost continu- 

 ously from the Hanging Hills of Meriden to Mt. Holyoke, in- 

 cludes (at least for the greater part of its course in Connecticut) 

 two sheets of trap, which are generally strongly contrasted 

 with each other, f The lower, or western, sheet is generally 

 highly amygdaloidal, containing chlorite, calcite, datolite, preh- 

 nite, and occasionally copper ores ; and does not usually show 

 any very distinct columnar structure. The upper, or eastern, 

 sheet is generally not amygdaloidal, and is generally much 

 more distinctly columnar than the former. The main crest of 

 the range is formed by the upper, or eastern, sheet of trap. 

 The lower, or western, sheet forms sometimes a lower parallel 

 ridge ("anterior range " of Percival). In other places the lower 

 sheet forms merely a terrace on the western face of the main 

 ridge. This terrace is very well marked on Talcott mountain, 

 a portion of the range lying west of Hartford, and much visited 

 on account of its magnificent prospect. 



At the village of TarifFville, in the northeast corner of the 

 town of Simsbury, the Farmington river cuts through the 



* Bulletin of the Museum of Comparative Zoology, vol. vii (Geological Series, 

 vol. i), no. ix. 



f Percival, Geology of Connecticut, pp. 369, 390. 



