GLACIAL EROSION IN THE GENESEE VALLEY SYSTEM 719 



in the direction or of necessary amount to turn the drainage from the depths 

 of Lake Ontario to the southwest. The buried Erigan and other tributary 

 valleys to that of Ontario are all against former drainage up the Dundas Val- 

 ley converging toward the west. 



ROOTS IN THE UNDER0LAY8 OF COAL 

 BY DAVID WHITE 



(Abstract) 



On a close inspection the floor, usually an "underclay," beneath the coal 

 beds in the American coal fields is, in the great majority of cases, found to 

 contain roots of vascular plants in their place of growth. The prevalent oc- 

 currence of such roots of various kinds, which are to be seen under the com- 

 mercially workable coals in all fields examined, whether of Tertiary, Mesozoic, 

 or Carboniferous age, clearly indicates that in most areas at least the coal 

 swamps were not too deeply submerged or inundated to permit vascular plants 

 to root and grow in place at the commencement of the formation of the mother 

 peat. In some cases evidence points also to the growth of arborescent vegeta- 

 tion on the surface of the growing peat. Such growth unquestionably occurred 

 on the partings of certain coals and was not infrequent in the roofs of the 

 submerged peats. 



OBJECTS AND METHODS OF PETROGRAPHIC DESCRIPTION 

 BY CHARLES P. BERKEY 



(Abstract) 



The object in most descriptions seems to be to lay a foundation for the con- 

 clusion, which is usually the name of the rock, yet there is almost always 

 much more detail than is used for such purpose. This is so prominent occa- 

 sionally that the most apparent object seems to be to record as much detail 

 as the investigator can determine. It is quite certain, however, that the real 

 object of many such studies is a quite different and much more complicated 

 matter — no less, indeed, than determining as fully as possible the life history 

 of the rock. The object, in other words, is rock interpretation instead of classi- 

 fication in its simplest form. 



Forms for recording data for use in the simpler cases were presented. 



