BUTLER COUNTY. 395 



The vegetation is imbedded in the clay very often, and part of it shows 

 that it has been subjected to rough, mechanical agencies. The frequent 

 presence of leaves and roots in or upon the deposit serves to show, how- 

 ever, that the source of the vegetation was not very far removed. The 

 north, bank of Elk Creek, opposite the mill at Miltonville, also gives a 

 fine exposure of the clay. At this point a peculiar modification of the 

 bowlder clay is found that deserves particular mention. It is a clay dis- 

 tinctly green in color, and, as shown by a single analysis of a specimen 

 obtained at this point, is very rich in potash and soda. The analysis 

 made by Prof. Wormley is here subjoined : 



Water combined 4.50 



Silicic acid 55.10 



Iron sesquioxide ■ 6.79 



Alumina 19.41 



Carbonate of lime 4.55 



Silicate of lime 3.55 



Magnesia 0.82 



Potash and soda 4.95 



99.67 



It will be seen that the elements above named, viz., potash and' soda, 

 are abundant enough here to make the clay a fertilizer of considerable 

 value. Vivianite, or phosphate of iron, is of frequent, perhaps constant, 

 occurrence in it. Vegetable matter is also always present. This green 

 clay has been more frequently met with in Warren and Butler counties 

 than elsewhere. 



The vegetable matter that is intermingled with the bowlder clay is to 

 be distinguished from that which is borne upon its surface. The pres- 

 ence of a buried soil of inter-glacial age has been repeatedly mentioned 

 in the reports on this Geological District. Examples of this ancient soil 

 are not wanting in Butler county. An interesting case of this sort is 

 recorded by David Christy, Psq., in his Letters on Geology, published in 

 1848. In the last letter of the series, page 5, he says : 



" Beneath onr Diluvium are occasional beds of ' hard-pan or very tough blue clay, 

 with imbedded pebbles.' I had my attention directed to this new and interesting fea- 

 ture of our Geology last summer by Robert Beckett, Esq., eight miles east of Oxford. 

 He called upon me to examine the stump of a tree standing erect in this deposit at a 

 point where a small stream is encroaching upon a bluff. The roots penetrated the hard- 

 pan in all directions. Twenty feet of Diluvium overlies it. We dug out the stump and 

 a part of the roots. Some years since, Mr. B., in digging a well twenty or thirty rods 

 distant from this point, at a depth often feet in the Diluvium, struck upon another small 



