28 Expedition to the 



rise through it. The smell of sulphuretted hydrogen is 

 perceptible at considerable distance about the spring, and a 

 piece of silver, held near the sunace of the water, was quick- 

 ly tarnished. The Silver Creek hills are of argillaceous sand- 

 stone, and secondary clay slate ; and this spring seems to be 

 placed near the meeting of the two strata. 



In the bed of the Ohio opposite Shippingsport, is a tabular 

 mass of rocks visible above water for great part of the year, 

 and called Corn Island. Onthehighestpartsof this, are remain- 

 ing some small portions, of the limestone stratum, which 

 appears in many places to have been worn through, and re- 

 moved by the river. Five or six acres of the surface of this 

 island are of the smooth compact argillaceous sand rock, 

 before mentioned, lying horizontally, and divided into squares 

 and paralellograms by the natural fissures. These fissures con- 

 tain some soil which supports, in the summer, a dense growth 

 of herbaceous plants. Among these we noticed the Hy- 

 pericum spluecrocarpum of Michaux (apparently not the plant 

 mentioned by Nuttail, under that name, which has been no- 

 ticed near Philadelphia, by Collins, and others, but without 

 doubt that originally described by Michaux). Two species 

 of Andropogon, the Panicum virgatum, Solanum nigrum, 

 Polygala verticillata, Leplanthus gramineus, Chenopodium 

 botrys, &c. The lower part of the island is covered with 

 loose sand} bearing some small cotton-wood and willow trees. 



The unenclosed grounds, about Louisville and Shippings- 

 port are extensive and afford pasturage to great numbers of 

 domestic animals. They are, however, much overrun with 

 luxuriant weeds. The Datura strammonium, which is com- 

 mon in every part of Ohio, is sometimes eaten by sheep, and 

 the spiny capsules of the seed, when about half ripened, we 

 have seen eaten with apparent avidity by cows. In addition 

 to this loathsome plant, the common may-weed (anthemis 

 cotula) has become abundant in all the waste grounds, to the 

 exclusion of the native plants. A few of these, which keep 

 their places with the greatest obstinacy by the road sides, 



