Rocky Mountains, 47 



The strata of sandstone containing the extensive beds of 

 coal which have been explored, about the Muddy river of 

 Illinois, are here divided transversely by the bed of the 

 Mississippi. The Grand Tower, the precipice opposite the 

 mouth of the Obrazo, containing the singular cavity called 

 the Devil's Oven, the Cornice Rock, and other remarkable 

 cliffs, are monuments indicating the great extent to which the 

 Mississippi has channelled its bed in these strata of horizon- 

 tal sandstone. 



The Grand Tower, from its form and situation, strongly 

 suggests the idea of a work of art. It is not impossible that 

 a bridge may be constructed here, for which this rock shall 

 serve as a pier. The shores, on both sides, are of substan- 

 tial and permanent rocks, which undoubtedly extend across, 

 forming the bed of the river. It is probable, however, that 

 the ledge of rocks called the two chains, extending down to 

 cape a la Bruche, presents greater facilities for the con- 

 struction of a bridge than this point, as the highlands there 

 approach nearer the river, and are less broken than in the 

 neighbourhood of the Grand Tower. The Ohio would also 

 admit of a bridge at the chains, which appear to be a con- 

 tinuation of the range of rocks here mentioned, crossing that 

 river fifteen miles above its confluence with the Mississippi. 

 We look forward to the time when these great works will 

 be completed. 



Compact and sparry limestones are frequent in this re- 

 gion ; but all the rocks seem to be acted upon with great 

 rapidity by currents of water. The country on the east side 

 of the Mississippi, back of fort Chartres, and about the river 

 St. Mary, is much broken by sink holes, having the form of 

 a funnel, and occasioned, probably, by the action of subter- 

 raneous streams of water finding their way through the fria- 

 ble sandstones, which underlay the deep and fertile soils in 

 those places. We passed in succession the mouths of the 

 river St. Mary, opposite to which is the fine settlement of 



