43.4 



Dr. M. C. Stopes. On the Four Visible 



coal, and particular attention has been paid to the " dull " and " bright " zones. 

 The/early and most excellent paper of Karsten (1826), in which the "matt" 

 and "glanz" coal layers were not only described but correlated with pi-e- 

 liminary chemical examinations, has been followed up by Bogers (1843) ; 

 Dawson (1859, 1866,^1871); Grand 'Eury (1882); Eenault , ^ (1882) ; 

 Von Giimbel (1834); Wethered (1885); Gresley (1892); Seyler (.1907) ; 

 Barsch (1908) ; Stevenson (1 911) ; Bowling (1911); Grout (1911); Lomax 

 (1911); Pringle (1911); White and Thiessen (1913); Hatch and Kastall 

 (1913); Grummitt and HickUng (1914); Jeffrey (1914); Lomax (1914, 

 1915) ; Strahan and Pollard (1915), as well as by many references of minor 

 importance. 



In these statements there is much difference of opinion, some authors 

 stating that plant structure is found only in the "dull," others that it is 

 found only in the " bright " coal. A detailed consideration of the views of 

 Bowling (1911), White and Thiessen (1913), and Hickling (1917) is essential, 

 but must be postponed to a later paper, when I hope to go into the matter 

 more fully. 



The lack of all preserved structure in " bright " coal maintained by various 

 authors, and its jelly-like nature, suggested by Bowling, for instance, in my 

 opinion indicate that the term " bright," as previously used, has covered both 

 the bright clarain and the brilliant vitrain, differentiated in the present work, 

 and also the secondary " brightness " resulting from natural agencies acting 

 on a coal like the Pentre. So that in the past some authors have meant 

 by " bright " the structureless brilliant vitrain, while others by the same 

 word have meant the bright clarain which so often is full of plant structure ; 

 hence has arisen the directly conflicting statements about the presence of 

 plant structure in " bright " and other coal. 



PAPERS QUOTED IN THE TEXT. 



Balfour, J. H. (1857) (read 1854). "On certain Vegetable Organisms found in Coal from 



Fordel," ' Trans. Eoy. Soc.,' vol. 21, pp. 187-193, Plates I and II. Edinbur^, 1857. 

 Barsch, O. (1908). "Die Pseudo-Kannel Kohle," Inaug. Diss., pp. 33, 2 text-figs., 



2 plates ; also in ' Jahr. k. Preuss. Geol. Landesanst. f iir 1908.' Berlin, 1908. 

 Dawson, J. W. (1859). "On the Vegetable Structures in Coal," ' Quart. Journ. Geol. 



Soc.,' vol. 15, pp. 626-641, Plates XVII-XX. London, 1859. 

 Dawson, J. W. (1866). " On the Conditions of the Deposition of Coal, inore especially 



as illustrated by the Coal -formation of Nova Scotia and New Brunswick," ' Quart. 



Journ. Geol. Soc.,' vol. 22, pp. 95-168, Plates V-XI. London, 1866. . 

 Dawson, J. W. (1871). " On Spore Cases in Coal," ' Ann. Nat. Hist.,' vol. 7, pp. 321-329, 



4 text-figs. London, 1871. 

 =Dowling, D. B. (1911). "The Formation of Coail," 'Proc. Trans. Roy. Soc.^ Caoada,' 

 ; vol. 4, pp. 23-35. 1910, ■r:,%l ■ :: . [ 



