188 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



lower. There are also many rapids, separated by pools or sluggish portions 

 of the stream. The elevation of the stream has been determined at many 

 points, but in the absence of a careful measurement of its length the rate 

 of fall is only approximately known. The portion of the river above the 

 point where it enters the old lake outlet, estimated to have a length of 100 

 miles, has a fall of about 300 feet, or 3 feet per mile. Railway levels and 

 canal surveys at the point where the river joins the old lake outlet show its 

 elevation to be very nearly 700 feet above tide, the altitudes reported 

 varying between 696 and 699 feet. The canah survey below Huntington 

 shows a fall of 32 feet to the mouth of the Salamonie, a distance of about 

 15 miles, and a fall of 34 feet between the mouth of the Salamonie and the 

 mouth of the Mississinawa, a distance of perhaps 20 miles. In the next 

 20 miles, to Loganspoi't, there is a fall of 50 feet. From Logansport to 

 Lafayette, a distance of about 50 miles, there is a fall of 77 feet. From 

 Lafayette to Attica, a distance of 25 miles, the fall is but 19 feet, and from 

 Attica to Covington, a distance of 20 miles, but 17 feet. From Covington 

 to Terre Haute, a distance of about 55 miles, there is a fall of only 22 

 feet, this being the lowest gradient for so long a section found on the, river. 

 From Terre Haute to the mouth of White River an accurate siirvey by the 

 United States Ai'my engineers shows a fall of 71.18 feet in a distance of 

 122.55 miles, or about 8 inches per mile. In this distance there are 13 

 riffles, each but a fraction of a mile in leng'th, which have a combined fall 

 of 17.86 feet. These reduce the fall of the 120 miles not embraced in the 

 riffles to 53.32 feet, or 5.33 inches per mile. The greatest fall at a riffle in 

 this section of the Wabash is at Grand Rapids, just above the mouth of 

 White River, where it amounts to 4.5 feet' The fall from the mouth of 

 the White is 65 feet in a distance of perhaps 90 miles by the windings 

 of the stream. 



' Thirteenth Ann. Eept. Geol. Surv. Indiana, 1883, pp. 69, 70. 



