FORESTRY SURVEY 211 



and Xorthfiekl Township and the northeast quarter of 

 Section 12, New Trier Township to the west. (See 

 Fig. 2. ) 



Section 1 of Xorthtield Township is incorporated in 

 Xew Trier Township, hence, since there is no Section 1 of 

 Xew Trier Township, Xorthfield 1 will be designated as 

 Xew Trier 1. The map of Gleucoe recently made by 

 Windes and Marsh has been used in this survey. The 

 dotted line to the east of this area, as seen in Fig. 2A, repre- 

 sents the topography as mapped by the State Geological 

 Survey of the State of Illinois many years ago. 



II. Physiography. 



A. Geology. 



This area lies at about the center of what the geologist 

 calls the "Evanston-Waukegan" region. It includes the 

 depression and the ridge at the most easterly edge of the 

 Valparaiso moraine. At this point it is composed of un- 

 stratified glacial drift over-lying Niagara limestone. This 

 drift is made up of a heterogeneous mixture of material 

 which is comprised of clay, sand, gravel, unweathered 

 pieces of rock, pebbles, cobblestones, and boulders. 



B. Physical Geography. 



The glacial drift forms a ridge (discussed as the up- 

 land) which is from a mile to a mile and a quarter in 

 width ; which extends in a northwest and southeast direc- 

 tion paralleling Lake Michigan; and which is from sixty 

 to eighty feet above the lake level. The glacial origin and 

 soil composition of the region account for the elevations 

 and depressions of both the upland and the lowland. The 

 slope of the ridge facing the lake is, on the whole, very 

 steep, whereas, the slope to the lowland on the west is a 

 very gradual one. The lowland lying parallel to the ridge 

 is known as the Skokie Swamp. This swamp was natur- 

 ally undrained, but the swamp is now ultimately drained 

 by a ditch which connects the Skokie Stream with the 

 East Fork of the Xortli Branch of the Chicagro Eiver. 



