Geology of Long Island. 353 



clays arc probably identical with the similar beds at Grossman's 

 in Huntington. 



Lake Eonkonkoma is in a basin of which the bottom is about 

 210 feet below the high ground on the south. Its southern bank 

 is composed of laminated sand streaked with oxide of iron, and 

 the rest of the shore appears to be formed of the same material. 

 At Crane Keck Point are bluffs, 60 feet high, of sand and gravel 

 containing masses of ferruginous sandstone of recent date. At 

 Herod's Point the bluffs consist of fine yellow sand and gravel, 

 slightly stratified, and dipping a few degrees south. Limonite 

 concretions tire here abundant. The bluffs at Friar's Head are 

 about 120 feet high, and consist of yellow stratified sand with 

 pebbles. Over these is a dune of yellowish drifted sand 90 feet 

 high, making the total hight of the peak 210 feet. On the west 

 side of Bobbin's Island is an exposure of blue clay overlaid by 

 laminated ferruginous sand. The depth of this clay-bed has not 

 been determined, but it is similar in appearance and quality to 

 some of the clays near Huntington, especially at Grossman's 

 brick-yard. A chalybeate spring issues from the laminated sand 

 on the shore, a little to the south of the clay-pit. The clay bed 

 appears to dip southward about 10° throughout the whole extent 

 of the island. Near the railroad between Southold and Green- 

 port are two brick-yards. At the more easterly of the two there 

 are various deposits of stratified sand and clay very much folded 

 and tilted. At this place the section exposed shows two parallel 

 folds, the axes of which trend a little N. of E. The upper stra- 

 tum of brown clay contains angular fragments of mica schist. 

 (See fig. 3.) At the other yard they are working a bed pre- 

 cisely similar to that just mentioned and also containing angular 

 fragments of rock. 



On Shelter Island are high hills of gravel with a thin covering 

 of till ; the highest point is about 180 feet above tide. West of 

 the village of Orient is a narrow isthmus of sand beach and salt 

 meadow, about a mile and a half long and not more than ten 

 feet above tide. East of this, on the north side of the peninsula, 

 Brown's Hills extend along the shore for a mile and a half, the 

 highest point being 128 feet above Long Island Sound. The 

 structure of these hills is difficult to determine, as extensive land 

 slides have occurred, and the slopes are covered with grass and 

 bushes. One exposure gave the following section: 



