Dawson.] 166 [March. 



coal formation of Nova Scotia. The " Upper coal-measures " of ray 

 papers on Nova Scotia are certainly wanting, and probably the 

 Sydney coal-field exhibits no beds higher than the middle of No. 4 

 of Logan's Joggin section. 



(5.) The whole of the coal-beds in the Joggin section belong to 

 the Upper and Middle coal-measures. It is quite incorrect to iden- 

 tify No. 6 of Logan's section with the Lower coal-measures. These 

 do not occur at the Joggins, but are found in Nova Scotia, as in 

 Virginia and Southern Pennsylvania, at the base of the system, 

 under the marine limestones. The Albert beds are the equivalents 

 of these Lower measures, and not of the Pictou coal. In my paper 

 on the Lower Carboniferous coal-measures (Journal of Geological So- 

 ciety of London, 1858), will be found a summary of the structure of 

 the Lower coal-measures, as shown at Horton BluflF, and elsewhere. 

 The term " true coal-measures," quoted by Mr. Lesley, does not 

 mean in my description, the Middle coal-measures, but merely that 

 part of them holding the workable coal-seams. 



(6.) Whatever may be the value of M. Lesquereux's applications 

 of the fossil flora to the identification of coal-seams in the West, I 

 am prepared to state, as the result of an extensive series of observa- 

 tions, still for the most part unpublished, that in Nova Scotia, the 

 flora is identical throughout the whole enormous thickness of the 

 Middle coal-measures, and that the diff"erences observable between 

 different seams, are attributable rather to difference of station and 

 conditions of preservation, than to lapse of time. It is, indeed, true, 

 as I have elsewhere explained, that the assemblages of species in the 

 Lower, Middle, and Upper coal-measures, may be distinguished ; but 

 within these groups the differences are purely local, and afford no 

 means for the identification of beds in distant places. 



(7.) I do not desire to offer any opinion on the questions raised 

 by some American geologists, as to the extension of the term carbo- 

 niferous to the Chemung group ; but I know as certain facts, that 

 the flora of the Lower coal-measures, under the marine limestones 

 and gypsums of Nova Scotia, is wholly carboniferous, and that the 

 flora, on which alone I consider myself competent to decide, of the 

 Chemung of New York, as now understood by Professor Hall, and 

 others, and also of the groups in Pennsylvania, named by Rogers, 

 Vergent, and Ponent (? IX and X of Mr. Lesley), is as decidedly 

 Devonian, and quite distinct from that of the carboniferous period.* 



* See Paper on Devonian Flora of Eastern America, Jour. Lond. Geol. Soc. 

 November, 1862. 



