AND OTHER VARIETIES OF COAL. 115 



that of a number of elongated yellow spots, so close together 

 in the same mass that the black matter between them forms 

 black striae parallel to the laminae of bedding. I have now 

 shown that thin horizontal and vertical sections of the coal 

 differ in the same manner and degree : horizontal sections 

 showing rounded yellow spots with dark-brown boundaries ; 

 and vertical sections, elongated yellow spots with dark-brown 

 boundaries, like dark stria? running in the direction of the 

 laminae of bedding of the coal. 



I stated at the outset that the coal will split with great ease 

 horizontally, but in no other direction. I would now point to 

 such vertical sections of coals as have been prepared without 

 having been cemented to the glass slide, for the most positive 

 proof that all such sections break up with great ease in the 

 direction of the striae parallel to the laminse of bedding, whilst 

 such a tendency to split is never observed in horizontal 

 sections. 



1 explain the tendency to split, which exists in all vertical 

 sections but never in horizontal ones, by the wide differences 

 in the microscopical characters of such sections ; and I think 

 it need scarcely be observed, that the characters presented by 

 the whole bed of coal, by small blocks when exam^ined by low 

 powers of the microscope as opaque objects, and by thin 

 sections examined by high powers, mutually illustrate and 

 explain each other. 



The only professedly complete account of the structure of 

 the Torbanehill as compared with other coals was given about 

 nine or ten months ago, in a paper read before the Micro- 

 scopical Society of London, and published in the last volume 

 of its Transactions. This paper, it is stated, was founded on 

 an examination of sections of most of the well-known varieties 

 of British coal, and supported by diawings and an extensive 

 series of preparations. Its conclusions, moreover, appear to 

 have received the assent of the Society ; for the President 

 stated in his published address that " the paper clearly de- 

 monstrates the presence, not merely of the remains of plants, 

 but of a peculiar woody structure in every description of coal, 

 and the absence of this peculiar structure in the mineral in 

 question." 



There appear to be two very important statements in that 

 paper, on which its conclusions are founded : — 1st. That in 

 the Torbanehill coal there is " no difference in structure 

 whichever way the section is made ;" and, 2nd, that a cubical 

 fragment of coal " on four of its six sides, in certain lights, 

 will exhibit a fibrous appearance, like a longitudinal section 

 of wood ;" again, that " transverse and longitudinal sections" 



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