AND OTHER VARIETIES OF COAL. 113 



is made up ; whilst the si'les and ends of the block will be 

 striated vertically , because they show the sides of the fibres 

 and vessels, which have been separated from each other in 

 their course. 



The block of coal presents rounded yellow spots above and 

 below, and horizontally striated sides and ends. Now, there 

 is this wide difference between the wood and coal — that wood 

 is composed of a multitude of fibres and vessels, arranged 

 vertically in a tree, and therefore cut across by a horizontal 

 section, and separated from each other so as to produce a ver- 

 tical striation on every vertical section, make it where you 

 may. Coal, on the other hand, consists of a multitude of 

 thin laminae, applied upon each other like the leaves of a 

 book. These laminae are made up of rounded yellow bodies, 

 flattened above and below, imbedded in a darker mass, and so 

 on every horizontal section these bodies are separated as one 

 would lift off the coins of a pile from each other ; whilst a 

 vertical section passes through them as such a section would 

 through the pile of coin. 



There is, therefore, as much resemblance between a block 

 of coal and one of wood as there is between a substance com- 

 posed of a series of laminae, and another made up of a number 

 of fibres closely packed together. 



We now turn to the appearances of tliin sections of the Tor- 

 hanehill coalj when examined by high powers of the micro- 

 scope. 



I think it will be obvious, from what has been said, that 

 the nature of any substance which can be examined by sec- 

 tions may be made out if such sections are made horizontally 

 at different depths, and vertically in several directions, so that 

 the planes of these vertical sections are at various angles to 

 each other. Or, if we cut sections from the top or bottom, 

 and from the side and end of such small blocks as those be- 

 fore named, these will enable us to judge of the nature of the 

 structures of which the mass is composed. 



Pieces of coal may be split horizontally from a block with a 

 knife and hammer with great ease for making thin horizontal 

 sections ; but, for vertical sections, a saw or the diamond- 

 wheel of the lapidary must be made use of. All sections of 

 the Torbanehill cannel may be ground sufficiently thin by the 

 hand without being cemented to a slip of glass in the ordinary 

 way. This plan is far more satisfactory in its results than 

 any other I haA e tried, and is much less likely to lead to error, 

 from destruction of tissue or obliteration of it by the materials 

 used in making the sections. I have 26 sections, horizontal 

 and vertical, which I prepared in this way from the same 



VOL. IIL I 



