OUTWASH OF THE MIAMI LOBE. 379 



known to be absent from portions of the plain a few miles distant from the 

 border, and quite uniformly present near the border of the moraine. The 

 plain occupies a part of the divide between the Whitewater and Great 

 Miami rivers, and stands much above the level of the gravel terraces in 

 these ^•alleys. The presence of gravel terraces in the valleys is evidence of 

 high altitude and good drainage, and, assuming the silts to be of the same 

 age as the ten-aces, it is evident that the conditions of slack drainage under 

 which they were deposited is not attributable to a low altitude of tlie 

 country. It seems instead to be due to the absence of drainage channels 

 adequate to connect the plain with these valleys. 



This interpretation naturally raises the question whether the silts which 

 cap the Illinoian drift sheet in the district outside the outer Wisconsin 

 moraine were also formed when the country was sufficiently high to afford 

 good drainage had channels been opened. Were these older silts confined 

 to poorly drained portions of the uplands, they might be very inconclusive 

 evidence of a low altitude of the country, but since they cover, as well, 

 districts which would have had good drainage were the altitude high, and 

 districts where no known obstruction to drainage could have existed, their 

 presence is considered conclusive evidence of low altitude. 



Several of the tributaries of Whitewater River, in Wayne Count}", Ind., 

 carry gravel plains which apparently find their head in this moraine 

 system. The head of the plain on East Fork is foimd in the middle member 

 near the point where it crosses the State line, the Ohio portion of the valle}' 

 being occupied by drift hillocks, while the Indiana portion carries a smooth 

 plain underlain by gravel. On Nolands and Greens forks there are broad 

 plains from the outer member southward and somewhat narrower plains 

 extending up to the middle member. It is probable that the main gravel 

 filling occurred while the ice sheet was forming the outer member. On 

 Martindale Fork the gravel plain finds its head at the outer member nearly 

 due east of Hagerstown. The plain along this stream is much broader near 

 its head than a few miles below, its width at the head being a mile or more. 

 This plain is called the "Walnut level," on account of the level surface and 

 the walnut timber whicli occupies it. On the west fork there is only a 

 narrow plain, that stream having been a less important glacial outlet than 

 Martindale Fork. 



With the exception of East Fork, all the tributaries of Whitewater are 



