Rocky Mountains. 29 



are the Sida abutibon and S. spinosa, and the verbena hastata, 

 while the thistles, Chrysanthemums, and Johnsworts so com- 

 mon about old fields, in New England, are not to be met 

 with. The Eleusine mucronata of Pursh, is one of the most 

 frequent grasses along the streets. 



The Silver Creek hills, are elevated about one hundred and 

 fifty, or two hundred feet above the level of the country in 

 the rear of JefFersonville. They form a continuous range, 

 crossing the country from north to south. On the Kentucky 

 side they constitute the commencement of a rugged and 

 barren district, called the Knobs, and extending far to the 

 south. At some remote period this range may have formed a 

 barrier, extending across what is now the immediate valley of 

 the Ohio, and retarding the retreat of the waters from the 

 tract above the falls. Coal occurs frequently in this range 

 of hills, on the north side of the Ohio; quarries have been 

 opened near the Blue river, in Indiana, about the two Pid- 

 geons, opposite the mouth of Green river, and in various 

 other places. 



The larger steam boats which run on the Mississippi, and 

 the Ohio, ascend usually no farther than Shippingsport, and 

 several of them remain at this place, during several months 

 of the summer, while the water is too low to admit their pas- 

 sing up and down the rivei*s. This time it is often necessa- 

 ry to spend in repairs of various kinds. The high steam en- 

 gines require frequent repairs, and in the difficult navigation of 

 the Mississippi the hulks of vessels are often injured. It fre- 

 quently happens that the boats, built at Pittsburgh, and other 

 places near the sources of the Ohio, are within three or four 

 years after they are launched, in a condition to require the plank- 

 ing of fne hulk to be replaced with new timber. These boats 

 are usually planked with the upland white-oak: we have been 

 informed that those boats which are built lower down on the 

 river, and of such timber as is found in the low grounds, 

 are more durable. 



