It forms the north fluke of the island and in more or less submerged condition continues as 

 Plum, Gull and Fishers islands finally going ashore at Watch hill in Rhode Island. 



The greater submergence of the easterly end of the island has flooded the intermorainal 

 space, splitting that end of the island into two flukes separated by Flanders, Little and Great 

 Peconic bays. Shelter and Gardiners Island sounds. In this interfluke area are Shelter and 

 Gardiners islands and numerous smaller bodies of land. 



These two Wisconsin moraines are thought to be due to the two latest glacial advances of 

 that age. An earlier and even more important ice advance formerly known as the Manhasset 

 and which some suppose to have passed clear over the entire island (15) is now thought 

 possibly to be Wisconsin. 



Still earlier glacial periods are represented by the outwash materials known as Jameco in 

 the western part of the island and by heavy deposits on the necks of the north shore and 

 Wheatley hills known as Manetto. 



All these complications in the glacial formations increase the diflJiculty of determining 

 the preglacial surface. 



It seems that in some measure the present surface topography and drainage channels 

 existing in it were controlled by the earlier topography, and for that reason careful study of 

 the present drainage system is necessary. 



The preglacial water parting appears over the greater part of the island to follow the 

 earlier moraine, but the present apparent water parting is, with two large and several small 

 exceptions, the newer moraine. 



In general the glacial material which forms nearly all of the surface of the island is so 

 porous that rainfall sinks into it rapidly and does not again emerge until near sea level. This 

 means that permanently flowing streams are not common but the drainage channels for such 

 streams are well developed and are shown on the Federal contour maps. At least one stream 

 that should be of considerable size disappears underground — Coram sink. Such conditions lead 

 to heavy ground water recharge, and undrained depressions must be particularly favorable 

 regions for such recharge. 



In the western part of the island where the youngest moraine is distant from the south 

 shore of the sound, the northward flowing streams start out in the normal direction perpen- 

 dicular to the moraine, but in most cases eventually turn sharply to run into the nearest bay. 

 The depressions of the bays themselves all extend to the Harbor Hill moraine. The necks 

 between the bays have rather irregular surfaces and the drainage of them also is irregular. 



South of the southerly moraine in the western counties, the streams run down the out- 

 wash plain to the Atlantic and fringing bays. These streams are simple, fairly straight over 

 considerable distances and with few branches. North and west of the root of Rockaway penin- 

 sula they are oriented on Jamaica bay. Further east many run nearly due south, but there is a 

 tendency for the upper reaches to run more nearly southwest, almost at an angle of 45 degrees 

 with the general trend of the contours and then to turn south at or near the 100 foot contour. 

 This is most marked in the case of East Meadow brook which rises in the intermorainal area 

 near Syosset and flows southwest to a point northwest of Freeport and then slightly east of 

 south passing through the village of Freeport into East bay. 



The intermorainal area drains through Gowanus and Newtown creeks. Flushing and Little 

 Neck bays, in that part where Harbor Hill moraine is south of Ronkonkoma moraine. At the 

 head of Manhasset bay the condition reverses from that point nearly to the Suffolk County line ; 

 the space in question drains to the south through numerous streams. At the Suffolk County line 



161 



