284 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of the disputed structures, together with the often convoluted and 

 folded condition of these under the same condition, constitutes a 

 strong argument against the algal nature of the latter, as it is hardly 

 conceivable that gelatinous Algae in mass, even if preserved by a bi- 

 tuminous antiseptic, should have escaped complete collapse under the 

 enormous and age-long pressure to which they have been subjected. 

 Even so resistant a substance as wood ultimately collapses completely 

 under pressure where it occurs as lignite. Figure 27, Plate 5, illustrates 

 the appearance of the boghead under consideration, as viewed under a 

 considerable magnification. The horizontal middle line of the figure 

 is occupied by part of a single convoluted individual oi Relnschia aus- 

 tralis. It is a noteworthy fact that the organisms of the later bog- 

 heads, such as those of Autun and New South Wales, are very much 

 larger in size than those found in the true Carboniferous coals of the 

 same general structure. This contrast is illustrated clearly by a com- 

 parison of Pila kentuchjana or Pila scotlca with Fila blbractensis or 

 Reinschia australis, the two latter species being many times the di- 

 mensions of those mentioned first. Figure 28, Plate 5, shows the 

 structure of a horizontal section of the boghead of New South Wales 

 as viewed under a low magnification. A little above the horizontal 

 middle line of the figure, two of the micro-organisms stand out with 

 particular clearness. Figure 29, Plate 5, shows one of these consider- 

 ably more highly magnified. The plane of section reveals both the 

 profile and face view of the organism, showing the alveolar structure 

 of the wall, found in all moderately well-preserved individuals. In 

 those which have lost the usual yellowish hue and have turned some 

 shade of brown, the structure has usually more or less completely 

 disappeared. 



The Structure of Coking Coals. 



It is a well-known fact that certain coals are well adapted for coking 

 purposes. In coals of this type when high temperatures are reached 

 in the coking oven, the coal melts and is transformed under appropri- 

 ate conditions into the substance known as coke, which is of course 

 virtually a mineral charcoal. The property of melting, when subjected 

 to heat, is one which is likewise characteristic of cannel and boghead 

 coals. It has been suggested in the case of the last that the gelosic 

 substance presented by the colonial framework of their supposed algal 

 components is responsible for the readiness of fusion at high tempera- 

 tures. Such an explanation is scarcely apposite in the case of the 

 similarly fusible cannel coals. Even if we accept the point of view of 

 Potonie and include the cannel coals likewise under the heading of 



