228 ILLINOIS ACADEMY OF SCIENCE 



The vegetation at the mouth of older ravines was uni- 

 formly that of the Populus-shrub and Juniperus-shrub 

 type of the lake bluff. Fig. 17 shows this type of ravine 

 mouth. Juniperiis virginiana and Juniperus communis 

 are the most abundant and characteristic species found 

 at the mouth of most ravines. This vegetation, in all the 

 ravines, extended back into the ravine farther on the 

 south-facing slope than on the north-facing slope. The 

 north-facing slope, in every case, was more mesophytic, 

 even to the very edge of the bluff, than the south-facing 

 slope. The south-facing bank in Ravine 6 (McLeish) is 

 recorded as being much steeper than the north facing 

 bank, and as being so seriously affected by wave erosion 

 as to have no vegetation at its base. Wherever erosion, or 

 unstable soil was found, as at the forking of Ravines 4 and 

 6 in N. T. 6, 47 and N. T. 8, 23, some distance inland, 

 Juniperus communis and Juniperus virginiana were grow- 

 ing there. 



b. Head. — The heads of the ravines had cut back no 

 farther than the upland. In nearly every case the gully 

 stage at the head of the ravine had been disturbed by man. 

 This modification had been carried back some distance 

 into the Ravines 1 and 3 in N. T. 6, D and E, because they 

 were being used as a part of the golf course. The lateral 

 gully, which is roughly V-shaped in cross section, but 

 whose slopes are more or less convex, may well represent 

 the very earliest stage of the ravine at its source in the 

 upland. Farther to the east the ravines began to have a 

 U-shaped appearance. It was noted in Ravine 4 (New- 

 hall) and Ravine 6 (McLeish) that the U-shaped area be- 

 came quite broad, up to a certain point, and then gradu- 

 ally merged into the deeper V-shaped ravine. The low 

 part of the U-shaped headland resembled the floodplain of 

 a river. This is well shown in Ravine 4 (Newhall), Fig. 

 IS. The stream at this point had not cut very deeply, but 

 the effects of erosion and deposition of material were seen 

 in a slight degree here. This illustrated the manner in 

 which base leveling is accomplished. In the Newhall 

 ravine the south facing slope seemed to have eroded more 

 than the opposite face, and the slope was on the whole a 

 more gentle one. Alternating temperatures may have 



