THIS GROUPING TENTATIVE. 71 



The grouping which I have given above should be considered as 

 merely tentative, and will probably need some modification hereafter ; it 

 may possibly need radical changes ; it would be very unsafe with our 

 present knowledge to assume otherwise; I know that* it will need some 

 interpolation in the Cretaceous groups in the southern part of the province. 

 I should have been pleased to have delayed its publication until the entire 

 province had been more thoroughly surveyed, but circumstances render it 

 necessary that I should do something more than make general statements 

 of the methods and results of the work which I have been doing. Congress 

 has appropriated money from year to year for the work on the representa- 

 tion of a few leading scientific men of the country that the work was being 

 done with reasonable skill and economy; but only the few who had time 

 and were willing to examine the work in manuscript at the office could 

 understand what we were doing, and it seemed but reasonable that a 

 demand should be made for the publication of some specific results. Hav- 

 ing concluded to commence the publication before the province was com- 

 pletely surveyed, it was absolutely necessary that some grouping of the 

 geological formations should be used. The map must be colored to show 

 the distribution of geological formations, arid of course names must be given 

 to the formations thus represented on the map, and a nomenclature is 

 necessary for discussion ; hence the publication of the table. But I shall 

 be willing to modify it to any extent as facts are collected which seem to 

 demand such a change, whether such facts are the results of my own labors 

 or those of others. Still I present the table with some degree of confidence. 

 The groups of rocks have been traced over broad areas, and in the district, 

 the geology of which I am to describe in this report, the grouping fully 

 represents the state of my knowledge. On account of the discussions which 

 have arisen concerning the age of certain beds of lignitic coal, the plane of 

 demarkation between the Cenozoic and Mesozoic may subject me to criti- 

 cism ; but, geologically, the plane is important, as it represents a decided 

 physical change, and it certainly harmonizes witli the opinion of paleontolo- 

 gists to a degree that is somewhat surprising. All of the plants described 

 by Professor Lesquereux and collected by himself and others within this 

 province have been referred by him to divisions in the Tertiary, and are 



