O74. i GEOLOGY OF OHIO. 
Soil and Timber.—The soil generally is dependent on the nature of the 
northern Drift. In this the various essentials, such as iron, lime, phos- 
phorus, silica, magnesia, alumina, and soda, are so thoroughly mixed and 
in so favorable proportions that the strength and fertility of the soil are 
very great. The depth of the soil has the same limit as the Drift itself, 
which is, on an average, about twenty-five feet. The soil is more gravelly 
and stony in the rolling tracts. The stones come partly from the under- 
lying rock, but mainly from the Drift. They are common along all the 
valleys of streams and creeks and in shallow ravines. ‘They are made 
to appear superficial by the washing away of the clayey parts of the Drift, 
and are not due to any Drift agency acting since the deposition of the 
great mass. The north-western part of the county has a heavy clayey 
soil, with some exceptions. This clayey, flat land is comparatively free 
from superficial bowlders. Very little gravel can be found except in the 
line of gravel knolls that passes north-westwardly through Radnor town- 
ship. The valleys of the streams, however, show a great many northern 
bowlders, as in other parts of the county. Besides these general charac- 
ters of the soil of the county, a great many modifications due to local 
causes will be seen in passing over the county. There are some marshy 
accumulations, which, when duly drained, are found to possess a soil of 
remarkable ammoniacal qualities, due to decaying vegetation. The 
alluvial river margins possess a characteristic soil, strongly contrasting 
with the generally clayey lands of the county. They are lighter and 
warmer, while they are annually renewed, like the countries of lower 
Hgypt, by the muddy waters of spring freshets, and are hence of ex- 
haustless fertility. | ; 
The whole county was originally wooded with deciduous trees, which 
were associated, in the eastern portion, with a few species of conifers. 
Rev. J. H. Creighton, of Delaware, has kindly furnished the following 
list of 
Trees, SHRUBS, AND Woopy Vines Founp GROWING IN DELAWARE CouNTY. 
Abies Canadensis............. sseseesee Michx..; Betullaymionareccsd cece eee tees Ly 
INCCTISACC MO ATIMUM eee aise acces cence Wang. Bignonia capreolata...............0-++ L. 
OO TADIOVADIID, cop scubosadosticboo oo00G6 bone: _ L. Crataegus cordata ...... saitetlenes etlowes Ait. 
NCL ABY, CATO Ulilexcwencessese nian teas ee Deve “ oxycantha...... Coteekenaeies lee 
Ampelopsis quinquefolia............ Michx. ty COCCINIEH ieee eal ee aennees L. 
ANI ES) 101/20 Ge Waesepanes obsoedendunindcobeoct Willd. ry LEV eA Seal aun ea eae er ANTIK 
Amelanchier Canadensis......... Monci& Gren, Cornusploridarsec. see et eee L. 
ANGHHTOMHOE, (EIKO) OF Gepcecieus Osco cb 06 00° Dunal. * (Canadensis uae L. 
Nesculusrolabraic.s..sesecsunedeonsr ers Willd. (iy pani Gulatar. st wveceteemeretees ‘L’Her. 
Benzoin odoriferum ................0 Nees. ‘c,  Vallternifolianyycccce cesses: L. 
pBetulanpapyiracCe a cuccorssiecvecetanes Aatan(?)e sCarya: albaiccs cuts sacseactcoceneeters Nutt. 
