DRIFT DIVISION. 
169 
unless where the inroads of the sea have washed the cliffs, and caused them to tumble or 
slide down to a lower level. The beach along most of the north shore of Long island is 
strewed with boulders from this cause. A little farther west, about one mile and a half west 
of Brown’s point, the effects of land-slides may be plainly seen. The waves undermine the 
cliffs, the land-springs make the subjacent clay slippery, and the masses crack off at the top 
of the cliff and slide down ; and the lighter materials being washed away, the boulders and 
blocks are left on the shore. This is illustrated in fig. 9, Plate 4. 
Many curious blocks of granite, gneiss and hornblende rock, occur on the north shore of 
Southold, showing quartz, granite, trap, etc. veins cutting through them. Plate 36, figs. 1, 
2, 3, 4, illustrate some of these. Fig. 1 is a sketch of a block of contorted hornblendic gneiss, 
with granite veins. It lies, or did lie, on the shore about north of Latham’s Hotel, half a mile 
west of Oysterpond point. Fig. 2, represents a block of contorted hornblende slate, contain¬ 
ing contorted branching veins of reddish granite of a moderately coarse grain, and a large vein 
of fine-grained reddish grey granite a foot wide. This block was observed on the north shore, 
on a point opposite to Greenport, and west of a lane leading to the shore from that village. 
Fig. 3 is a sketch of granitic gneiss, not fissile, and very slightly striped by the arrangement 
of its materials, containing a contorted vein of fissile hornblende slate ! This block was in 
the water north-northwest of Oysterpond Point Hotel, about three-fourths of a niile west of 
Oysterpond point. 
On the beach at Oysterpond point, white siliceous sand, red garnet sand, black iron sand, 
pebbles of greasy quartz, feldspar, porphyry, greenstone, granite, gneiss, mica slate and 
quartz rock (granular), are found. Boulders of granite and gneiss, and some few of other 
rocks, are found at the point, and on the north shore west of it. This point of land is washing 
away continually, and this subject is spoken of under Alluvion ; but as Dr. Mitchill’s observa¬ 
tions on this locality in the year 1800 have come to my notice since that article was printed, 
the following extract from his observations is here introduced : “There can be no reasonable 
doubt that this detached piece of land (Plumb island) was formerly connected with Long 
island at Oysterpond point, from which it is now distant about three quarters of a mile in a 
northeasterly direction. The Indian tradition is, that the distance was formerly very small.”* 
The distance is now probably more than a mile, perhaps a mile and a half. The shore of 
Plumb island opposite is also washing away. 
Some of the erratic blocks of Long island are of great size. One on Mr. Latham’s farm 
at Oysterpond point was mostly blasted to pieces, and made into a stone fence. He stated 
that the fragments made eighty rods (one-fourth of a mile) of stone fence, four feet high. A 
portion still remains in the ground. The portion used must have weighed more than nine 
hundred tons. 
At Horton’s point in Southold, the boulders and blocks of granite and gneiss cover the 
beach under the cliff. They fall from the upper stratum, like the boulder stratum of Brown’s 
Geol. 1st Dist. 
Medical Repository, New-York, 1802, Vol. 5, p. 214. 
22 
