OUTER MORAINE OF THE MIAMI LOBE. 345 



usually but 20 to 25 feet, rarely 40 feet, from the surface, and it is thoug-Jit 

 to constitute, as a rule, the surface of the older or lUinoian drift sheet. 

 Apparently this slight depth represents the usual thickness of the early 

 Wisconsin drift in this region, for it is not over 25 feet on the moraine at 

 Martinsville and Marshall, and may be even less on the inner plain. 



At Martinsville many wells strike considerable vegetal inaterial, wood, 

 soil, etc., at about 20 feet, but occasionally as low as 40 feet. Wells in this 

 village 40 to 45 feet deep do not reach rock. In some wells inflammable 

 gas issues at a depth of from 30 to 40 feet, and is perhaps derived from the 

 vegetal deposits of the drift. The drift there is mainly till, both- above and 

 below the buried soil. 



Orton has reported that at Marshall 11 out of 20 -wells struck a buried 

 soil or vegetal material at slight depth. The drift at this place extends 

 deeper than the horizon of the soil, since wells 25 to 30 feet deep on low 

 ground, as well as those on knolls, fail to reach rock. 



Near Wilmington the distance to rock on surfaces having no marked 

 diff'erence in altitude ranges from a mere trace up to 80 feet or more, there 

 being an outcrop of rock just east of the city, while on ground equally low 

 within the city limits 60 feet of drift is not uncommon, and the gas-well 

 boring north of the city, on ground but little higher, penetrates about 80 

 feet of drift. The late L. B. Welch, of Wilmington, has ascertained that 

 wells in Wilmington, where drift is 60 feet deep, penetrate about equal 

 amounts of older drift and newer, and the older, i. e., that below the buried 

 soil, is drier and much more difficult to penetrate than the newer, probably 

 because of a partial cementation. Excellent exposures of the buried soil 

 are found along Lytles Creek in the south part of Wilmington. The soil 

 is 2 to 6 feet in thickness and of very dark color. It is overlain by 15 or 

 20 feet of Wisconsin till and underlain by about the same amount of lUi- 

 noian till. There is a small amount of white clay resting on the soil, but in 

 most of the exposures the clay was removed before the Wisconsin till was 

 laid down, so that the till commonly rests directly on the soil. The till 

 below the black soil is oxidized to a depth of 10 or 12 feet, below which it 

 is of a blue color. It is on Lytles Creek, a few rods below the place 

 where the buried soil is exposed, that strise were found beneath the Illinoian 

 drift. They bear S. 32° W., or in about the same direction as the Wisconsin 

 ice movemeiit. As above noted (p. 326), they bear strongly upon tlie inter- 



