SECTIONAL TRANSACTIONS.— C. 353 



reason to hope that precision may be possible on certain horizons after much 

 work. 



Dr. Slater and his assistants have, however, of recent years greatly 

 accelerated their methods by examining polished surfaces of the coal by 

 incident light, and at the same time simplifying their diagrams. In this way 

 they have succeeded in comparing a number of sections within the Yorkshire 

 field and getting comparable results with the same seam. The particulars 

 are, however, as yet unpublished. 



Dr. Raistrick's method by separation of microspores is a distinct advance 

 in that it enables abundant material to be examined, so that seams of supposed 

 identity can be shown to be not merely like one another but different from 

 all others with which they might be confused. The method is being ex- 

 haustively tested. The results are extremely promising, but there are a 

 number of pitfalls which still need careful investigation. Methods of treat- 

 ment must be carefully standardised if comparable results are to be obtained ; 

 the classification of spores is far from satisfactory ; the personal factor in 

 observations enters in some degree into the results, and finally, if there is a 

 marked change in the physical character of the seam the spore content varies 

 accordingly. 



Dr. Raistrick's results in Northumberland, however, seem to show that 

 quite reliable correlation can be obtained within the field, and those investi- 

 gations which he has up to the present made in Lancashire promise similar 

 results. 



Dr. Emily Dix. 



In many cases, the non-marine and marine fossils form the most reliable 

 indices for detailed correlation, yet at certain horizons the plants are so 

 characteristic that they are quite as important for zonal purposes as the 

 non-marine shells. In areas where their use is difficult, especially in the 

 upper measures, the evidence afforded by the plants is particularly important. 

 Dr. Kidston showed that plants could be used for subdividing rocks of coal 

 measure age ; subsequently further studies on fossil floras have substantiated 

 this view. The Upper Carboniferous rocks of South Wales can be divided 

 into nine floral zones (two of which are confined to the Millstone Grit). In 

 defining each zone the whole of the floral assemblage has been considered, 

 although certain species have much greater value for purposes of correlation 

 than others. In general the succession of plants in the South Wales Coal- 

 field agrees very closely with that of other coalfields in Great Britain, and 

 also with that of corresponding strata on the Continent and in North 

 America, as shown by the work of Bertrand, Gothan, Jongmans, Renier, 

 Darrah and others. 



For many years it was recognised that the correlation of the coal measures 

 based on the faunas was not in agreement with the results obtained by, 

 workers on the plants. This discrepancy does not exist. In the upper part 

 of the Millstone Grit and the lower part of the Coal Measures distinctive 

 floras are found in every coalfield in Britain where the sequence is known, 

 which are comparable with those found in the zone of Neuropteris schlehani 

 and Sphenopteris hoeninghausi on the Continent. 



It appears that certain floral changes took place more or less simul- 

 taneously over the whole of Europe and North America. Perhaps the most 

 striking floral change takes place at the entry of the rich Staffordian flora of 

 Kidston (Flora G (Dix)). This marked change has been emphasised by 

 Prof. Trueman and the writer, and it has been suggested that the West- 

 phalian can be divided into lower and upper divisions at this level, and that 



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