424 GLACIAL GKAVELS OF MAINE. 



stratification, yet plainly are composed of water-waslied material. My 

 conclusion is that where the whole of a ridge of till, from which the finer 

 detritus has plainly been washed by water, has lost all signs of stratifica- 

 tion and has a pellmell structure, the best interpretation is that it was 

 deposited upon the ice in a superficial or englacial channel, and that when 

 the ice underneath the sediment melted, the gravel slid down irregularly 

 and the original stratification was lost. 



A well-marked instance of an osar with pellmell stnicture is Indian 

 Ridge, at Andover, Massachusetts, described many years ago by Dr. Edward 

 Hitchcock, and more recently and fully by Prof Gr. F. Wright. Professor 

 Dana has referred to this ridge as a moraine. But the material is slightly 

 polished by water and the finest parts of the till have been washed out of 

 it. It is not the ordinary till of the region, but the residue after a portion 

 has been removed by water. There has also been some water transporta- 

 tion, but not much, or the stones would be more polished. Moreover, it 

 stands in substantially the same relation to the plain of stratified sand and 

 gravel near Ballardvale as the osars of Maine stand to the deltas deposited 

 in glacial lakes. In a sense all glacial gravels are morainal. It is not 

 proved that Indian Ridge was bodily transported horizontally by the ice 

 after its deposition, yet this may have happened. If so, it will be a dis- 

 puted question whether to term it a moraine or an osar. The criterion of 

 distinction between the till and the glacial sediments proposed in this report 

 is that the one was brought to its present position by the ice and the other 

 by water. In case of ice transportation of Indian Ridge as a whole, we 

 would have a mingling of the two processes. But where a transported 

 ridge maintained its individuality as a mass of water-washed matter distinct 

 from the adjacent till, I should not hesitate to apply the term " osar" to it. 

 It is certain that few, if any, of the osars of Maine were thus bodily trans- 

 ported by the ice, at least in the last stages of their development. Where 

 an osar is stratified in some parts of its course and is pellmell in others, 

 there can have been no bodily transportation on any theory yet suggested. 



In general we remark : A stratified internal structure is consistent with 

 either subglacial or superglacial streams. Pellmell structure of a large 

 mass of glacial gravel strongly favors the hypothesis that it was deposited 

 on the ice, not beneath it. Quaquaversal stratification of a cone (not due 

 to surface wash by the sea waves) is in favor of the theory that the gravel 



