56 SECTIONAL^ADDRESSES. 



as any of the layers, and may recur several times in an inch of coal. 

 It would be diliicult to imagine reafforestation so frequent and so 

 necessarily extensive. 



These varying types of material recurrent in the thickness of the 

 coal-seams leave us, it is true, some unsolved problems, but they 

 present us with a sufficient basis of fact to enable imagination to call 

 up the general conditions of coal-formation. 



Let us now imagine a great expanse of newly formed or forming 

 mud or sand flats. Over this area semi-aquatic plants creep out and 

 establish themselves, their dead remains and windfalls gradually 

 accumulating into a bed of decaying vegetable debris upon which other 

 plants — not necessarily of the same type — follow. With varying and 

 perhaps recurrent conditions of drainage and moistui'e one flora succeeds 

 another. Some day it should be possible to map out the ecology of 

 the coalfields at the time of the formation of the coal-seams in some- 

 what the same way that Dr. W. G. Smith has portrayed the dis- 

 tribution of plant associations on the surface of Yorkshire to-day, and 

 we may be able to trace the chronological plant-sequence, as has been 

 done for modern peat-bogs. This result will be achieved through the 

 study with the microscope of thin sections of coal — especially serial 

 sections extending from base to summit of a particular seam. Such 

 a method of study was first attempted by Wethered, but it was not 

 until mechanical methods of section-making were brought to perfection 

 by Mr. James Lomax that complete success was attained. 



There are now available for study — thanks to the interest taken in 

 these inquiries by coal-owners in the Yorkshire Coalfield — six complete 

 series of sections taken from our great Barnsley Bed at geographical 

 intervals of about four or five miles. When the whole coalfield is 

 spanned by a suite of such series a great addition will be made to our 

 knov/ledge of the swamp-forests of the Coal Measures. 



Lomax declares that there is a general succession of constituents 

 recognisable in many seams, which must be related to the predilections 

 of the plants concerned in the matter of drainage and other factors. 

 He says : 



' Usually the lower part of a seam consists of a bed of very fine 

 humus or mixture of leaf-like matter, with hei'e and there portions of 

 stems, fructiferous organs, &c., probably derived from the remains of 

 small, more or less delicate, plants, and forming soft bright-looking beds 

 of coal. Ascending upwards in the seam other plant remains are to 

 be found, some belonging to the Gymnosperms. 



' Other remains are the Lycopods (Club-mosses), which as time went 

 on increased both in size and vigour, ultimately crowding out almost 

 every other kind of vegetation, and becoming the predominant plants 

 of their time. 



' The various changes, progress, and deterioration can be traced until 

 ultimately the plant life represented in the top of the seam is found 

 to be practically identical with that at the bottom.' 



Some such sequence is, of course, to be expected. When a bed 

 of mud, sand, or limestone emerges from below water-level to be a 

 land sm-face it could not be expected that every type of plant-life could 



