Geology of Martha's Vineyard. 241* 



Vineyard ; and form a part of the south east barrier of Buz- 

 zards Bay. They contain a few scattered inhabitants. 



In my route from the city of Boston, I passed over the 

 well known puddingstone of Roxbury and Dorchester; the 

 argillite and greenstone of Quincy; the sienite and sienitic 

 granite of Braintreeand Weymouth, with its beautiful dykes 

 of basalt, or greenstone; the gray wacke slate? of Abington ; 

 the diluvium of East and South Bridgewater ; the gray 

 wacke slate, diluvium and singular talcous rock, containing 

 feldspar, of Middleboro ; and struck at New Bedford, upon 

 mica slate, hornblende slate, and gneiss, inter-stratified, and 

 containing beds and veins of granite. In sailing out of New 

 Bedford harbour, these latter rocks appeared occasionally, 

 for several miles along the shore ; and I was led to antici- 

 pate their continuance as far as Elizabeth Islands and Mar* 

 tha's Vineyard : but on passing the former, I perceived a 

 diluvial coat to be spread over their somewhat hilly surface ; 

 while the shores, in many places, exhibited steep declivities 

 of sand. And on reaching the north western shore of Mar- 

 tha's vineyard, I found its aspect to be very similar These 

 islands so far as I have examined them, appear to be made 

 up of the three following formations : 1 Alluvial : 2 Diluvi- 

 al : 3 Plastic Glay. I use these terms in the Modern re- 

 stricted sense ; that is, as the latest writers employ them, in 

 describing the strata of England and France. I take for a 

 standard, the late work of Conybeare and Phillips, on the 

 geology of England and Wales. 



1 Alluvial. 



This formation occupies a considerable portion of the 

 southern part of the Vineyard ; reaching in some places, 

 even beyond the centre of the island. Where I crossed it, 

 it consists of a perfectly level, sandy tract, uninhabited and 

 uninhabitable. I have rarely seen as extensive a region, 

 that was so cheerless and barren. It is covered by stinted 

 shrub oaks, rarely exceeding five feet in height, and when I 

 saw them, they were entirely leafless, presenting to the eye, 

 a cheerless, wintry waste. On my right as I crossed this 

 plain, at a distance, appeared a ridge of high land and roun- 

 ded eminences : but on my left, nothing was to be seen, ex- 

 cept this uniform unrelieved barrenness. I was immedi- 



V.ol VII. No. 2 31 



