22 TRANSACTIONS OF THE [oct. 17, 
a distance of one hundred and seventy miles, from New York to 
Vermont, over an area of at least eight hundred square miles, 
With this limestone, usually the bottom layer of the series, are 
commonly associated beds of mica-schist, mica-slate, and gneiss, 
underlying, interstratified, or overlying. Next above, comes 
a layer of quartzyte (often passing into gneiss), then one of 
schist or gneiss, then another layer of quartzyte (that which 
forms the crest of Monument Mountain, north of Great Bar- 
rington), and then a series of thin beds of gneiss, schist, quart- 
zyte, and limestone (best shown at Three Mile Ridge, four 
miles east of Great Barrington). 
The whole series is fortunately crumpled up everywhere into 
sharp folds, which, by the erosion of ages, have been worn 
down or cut into at many points, thus bringing up the lime- 
stone layer into view here and there. In this way it crops out 
first as a coarse marble, at a point south of Pawling, in Dutch- 
ess County, New York; then at many points, becoming finer 
grained in its progress northward, over a stretch of seventy 
miles, to Pittsfield, in Western Massachusetts, along the Hou- 
satonic and two neighboring valleys; and then, for a hundred 
miles farther, in fine soft marbles, to a point twenty miles 
north of Rutland, in Vermont. 
The uniform lithological character of this limestone-sheet is 
in general strongly marked; although this is attended by a con- 
siderable variation in texture, from grains 1 mm. or less in 
diameter, in the northern part of the belt, to grains over 1 cm. 
in diameter near its southern extremity. Its color is predomi- 
nantly white, with light bluish or grayish bands, variously dis- 
posed and occasionally overspreading and darkening the entire 
material. These darker variegations consist of drawn-out plates 
and films of clay-slate or hydromica-slate, in which, where thick- 
est, a small proportion of iron pyrites is sometimes concen- 
trated. 
The employment of the material as an ornamental marble, 
or as a building-stone at many localities, has led to abundant 
determinations of its weight, compressive strength, and struc- 
ture, which have been found to vary but little along its course 
of outcrop. 
The accessory minerals it contains are usually the same— 
tremolite, magnesian mica, rutile, tourmaline, etc., together 
with a species of iron pyrites which, in many localities, from 
New York to Vermont, is unfortunately subject to ready de- 
composition. 
The common distribution along the main belt of a rather 
pure Jimestone, only occasionally somewhat magnesian, may be 
inferred, even by the traveller, from the numerous kilns in 
