PHYSICAL GEOGRAPHY OF THE CAPE COLONY. 



251 



Carbon 



Van Vyk *. 



Van Zyl *. 



Indwe t. 



69-72 



63-74 



61-021 



Hydrogen ... 



2-98 



2-81 



3-208 



Oxygen ... -i 

 Nitrogen J 



496 



4-65 



2-178 

 2-190 



Sulphur 



0-97 



0-76 



0-434 



Ash 



22-34 



28-80 



30-320 





The composition of all these coals, excluding the ash, is almost 

 exactly the same. The Indwe coal is free-burning ; the other two 

 coals light with so much difficulty that it is said they will not burn 

 at all. I hope that I have got some way towards detecting a 

 peculiarity in physical structure which may account for this 

 difference. Some of Yan Vyk's coal was coarsely powdered and 

 heated in a platinum spoon before a blowpipe. It burnt slowly 

 without flame, and left a light-brown residue, the fragments being 

 unaltered in shape by the heating. Under a power of 40 diameters 

 the brown fragments are seen to have a curious reticulated struc- 

 ture. There are a number of thin wavy plates which enclose 

 lenticular cavities or boxes. Some boxes are empty, others contain 

 a black substance ; this is probably the carbonaceous part of the 

 coal, which has been burnt out of the empty boxes, while in the 

 case of the others the combustion has been incomplete. It looks 

 as if the carbonaceous matter had been broken up into small frag- 

 ments each of which is enclosed in a box of incombustible material J. 

 Such a result would be produced if vegetable matter floated in 

 water long enough to be disintegrated, and if each fragment, as it 

 sank slowly, became invested with a coating of mud. I did not 

 succeed in detecting any similar structure in Yan Zyl's coal ; but 

 the experiment is one in which success is attained only by some- 

 what of a lucky combination of accidents ; pounding too roughly 

 or an excess of heat would be very liable to destroy so delicate a 

 structure. 



In the hope of getting some further insight into the nature of 

 these mud-films, the surface of one was scrubbed with a clean brush 

 and hot distilled water. The mud obtained was dried and ignited 

 for five hours in a platinum crucible over a Bunsen-burner. The 

 incombustible residue consisted of two parts. One consisted of dull 

 whitish, tufaceous-like shreds, which dissolved with effervesence in 

 cold dilute hydrochloric acid. In view of the large deposits of 

 calcareous tufa which cover so much of the surface in this part of 



* Analyses by Mr. C. H. Bothamley, Assistant-Lecturer in Chemistry, 

 Yorkshire College, Leeds. 



t Mr. North's Eeport (quoted above), p. 10. 



I Professor Williamson was good enough to attempt a microscopic exami- 

 nation of this coal, but he was unable to grind a section thin enough to be 

 transparent. 



8 2 



