in the Counties of New-Haven and Litchfield. 209 
to a cylindrical form, is placed horizontally, and connected 
with machinery moved by water; it is thus made to rotate 
rapidly, and at the same time a proper tool is so applied to it, 
as to cut the spiral groove, and of course to leave prominent 
a corresponding spiral thread. 
Geological and picturesque features of the country. A 
waterfall. 
August 28,1817 —Finding myself in the midst of a 
country, whose mineralogy and geology appeared very 
interesting, I took advantage of a bright morning, and was 
in my gig ata very early hour. 
- Lofty hills and mountains,—steep and abrupt vallies and 
lively water-courses surrounded me on every side. I proceed- 
ed between hills of gneiss on my way to the iron mines 
of Salisbury. Fragments of dolomite and other forms of 
white primitive limestone began to abound along the road, 
and many of them were full of crystals of tremolite (the 
grammatite of Haiiy ;) they afforded such beautiful speci- 
mens that I could not resist the temptation to descend very 
often with my hammer. It was impossible to doubt that a 
great change in the geological features of the country would 
soon be observed, and that primitive limestone must soon oc- 
cur an place. 
Accordingly, before I had gone over the four miles which 
brought me to the Housatonick river, ledges of white lime- 
stone began to make their appearance at some distance from 
the road on the right, but gneiss was the last rock which 
occurred before crossing the river. 
The scenery was altogether wild, and possessed of 
very considerable grandeur. A quarter of a mile above the 
bridge, the river, here of considerable width, falls over a 
ledge of limestone (as itappeared to me at the nearest point 
of approach) with clouds of spray, ina white and almost 
unbroken sheet of water, and with the thundering noise of a 
cataract. I believe the fall is about thirty feet, and being all 
at one leap, the effect is very fine. 
Al Furnace. 
Between the fall and the bridge, a furnace of very cen- 
siderable extent was in full operation, and its clouds of black 
