18 Microscopic Characters of some Peculiar Forms of Coke. 



series of regular ridges passing obliquely outwards from a 

 middle line, which is either a groove, a ridge, or an irregular 

 ridge broken up into segments, as in the figure. This speci- 

 men is not cylindrical, but flattened, and has the appearance of 

 being two " hairs " placed side by side and joined to each other 

 at intervals. 



Specimens such as that given in fig. 11 do not seem to be so 

 common as some of the others. At first sight this appears 

 like a number of shots irregularly massed together ; but upon 

 closer inspection it will be seen that it consists, not of spheres, 

 but of very sharply defined hemispheres, the flat surfaces of 

 which arc uniformly turned inwards. 



Fig. 10 represents one of a number of forms which resemble 

 minute drumsticks — the knobs of each consisting of a tangled 

 mass of hairs and granules, and giving one the impression that 

 it has been caused by an explosion. 



With regard to the internal structure of this hair-like coke, 

 some of the fibres when broken open appear vesicular, while 

 others are solid and have much the aspect of a piece of char- 

 coal. The solid "hairs" must, I think, have been formed in 

 the first place as threads of semifluid carbonaceous material, 

 and subsequently decomposed by being further heated. There is 

 little room for doubting that the vesicular kind of " hairs " have 

 been produced by a process of bubbling, caused by gases 

 forcing their way through the semifluid carbonaceous matters 

 in the manner intimated by Dr. Percy (loc. cit. p. 421). It is not 

 difficult to imagine that such simple forms as those represented 

 in figs. 3, 4, and 5 may have been formed in either of these 

 two ways, or to understand how a series of bubbles formed ra- 

 pidly one beyond another might produce the moniliform cha- 

 racter of fig. 7, although one would scarcely have expected it 

 to be so regular ; but it is not easy to imagine how either pro- 

 cess could have produced the regular oblique markings of 

 fig. 9, or the bundles of tubes (?) seen in the specimen fig. 8. 

 With regard to the hemispheres (fig. 11), one would like to 

 know how it is that they are so sharply defined as AaZ/-spheres, 

 instead of being spheres (or nearly so), as we might have ex- 

 pected them to be — that is, supposing that they are bubbles. 



The figures which are given do not represent all the forms 

 which may be seen ; they were merely taken as good illustra- 

 tive examples, the variations and intermediate conditions being 

 well nigh endless. 



A specimen of hair-like coke may be seen in the Museum of 

 Practical Geology; but it does not exhibit the various forms 

 alluded to above, in so marked a manner as that in the pos- 

 session of Dr. Percy. 



