JEFFREY. — NATURE OF SOME SUPPOSED ALGAL COALS. 285 



algal or sapropelic coals, there appears to be considerable difficulty in 

 accounting for the fact that the supposed algal constituents in true 

 cannel coals are either insignificant in proportion to the unquestion- 

 able spores or are entirely absent. With a view to putting the valid- 

 ity of the algal hypothesis of the origin of fusible coals to the test, I 

 have examined a number of coking coals microscopically, by the same 

 general methods as those used in the case of cannels and bogheads. 

 It is not my intention at the present time to attempt to describe the 

 composition of coking coals as seen under the microscope, but certain 

 facts, however, may be appropriately referred to. In general coking 

 coals consist of dull and bright layers, which vary as to their relative 

 thickness and general distribution. It has been found in those cases 

 examined that the dull portions of coking coals represent wood in a 

 more or less modified, but still clearly recognizable condition, while the 

 bright parts of such coals are composed of wood in a high degree of 

 modification and disintegration. Figure 30, Plate 5, shows a horizontal 

 section through the layering of the dull region of a coking coal, known 

 commercially as " No. I. Pennsylvania Coking." In the middle vertical 

 line of the figure may be seen the end of a wood tracheid, showing un- 

 questionable bordered pits. I have found similar appearances in the 

 dull layers of other coking coals, notably Pocahontas coal. The bright 

 parts of coking coal present the same composition with a much greater 

 modification, both structural and chemical, of the wood elements. It 

 is thus apparent that there is no necessary relation between the fusibil- 

 ity of coal and the presence of organisms of an algal nature, since can- 

 nel coal, which has few or none of the organisms, considered to be 

 Algae, and coking coal, which is made up entirely of the remains of 

 wood, both are fusible coals. It should be added that the structures 

 appearing to the right and left of the vertical middle line are likewise 

 wood elements, although they are not clearly recognizable as such in 

 figure 30, Plate 5. 



Conclusions. 



It is appropriate, after the description of the organization of bog- 

 head coals from various parts of the world and from different levels of 

 the Paleozoic given in the foregoing paragraphs, to discuss the algal 

 hypothesis of the origin of these coals. It may be pointed out that 

 there is unanimity among the various observers as to the common and 

 similar organization of the structures present in these coals. It follows 

 that if the best preserved ones and those which by reason of their size 

 are most easily studied in thin sections of coal, turn out not to be of 

 algal affinities, that a similar conclusion must be applied to the re- 



