208 
GEOLOGY: E. C. JEFFREY 
English coals containing *coal balls/ which the author owes to the 
kindness of Dr. Marie Stopes of the University of London whose in- 
vestigations on the origin of these petrifactions are known to all (4). 
Through the kindness of Dr. M. Zalessky of the Comite Geologique of 
Petrograd similar coals have been secured from the great Donetz coal 
fields of Russia. To the administration of the Geologische Landesanstalt 
of Prussia, the author owes material of the dolomitic so-called ^Torf- 
kohle' of Westphalia. It will be seen that there has been no dearth of 
appropriate materials for investigation. The organization in every 
case has been proved to be the same and is that shown in figure 3. 
This represents a substance which is composed of darker and lighter 
bands, more or less interrupted by cracks in the matrix of the coal. 
The lighter zones correspond to modified woody material present in the 
original accumulation and the darker stripes to more perishable matter, 
to judge from the situation in the bottom deposits of existing lakes, 
often consisting of the excrements of aquatic animals, such as molluscs, 
fish and amphibia, as well as the more deHcate and destructible parts of 
plants. Where the woody material is massive the resulting coal is 
frequently quite homogeneous in its character and corresponds to the 
lighter substance shown in figure 3. The type of organization shown in 
the figure under discussion is frequent in the higher grade coking coals 
of the United States, namely those of Pennsylvania and Virginia. Prac- 
tically no petrified coals however have yet been described for the North 
American continent. 
Figure 4 exempHfies the organization of a typical coal from Lan- 
cashire, England. This illustration shows the presence of a large number 
of light bodies, which are flattened spores. A very large spore (a so- 
called megaspore) is seen in the lower region, while innumerable smaller 
ones are scattered throughout the substance of the coal. In addition 
to the spores are seen bands of darker hue corresponding to much modi- 
fied wood and black zones which represent the more perishable parts of 
the original materials from which the combustible has been derived. 
The bands of the coal under discussion have their counterpart in similar 
structures shown in figure 3. In the coal ball however the innumerable 
spores of figure 4 are conspicuous by their absence. It will at once be 
apparent to the reader that ordinary bituminous coals are much more 
like cannels in their organization than like that of the seams in which 
the petrifactions known as 'coal balls' occur. It is thus clear that ordi- 
nary bituminous coal must, if structure is a reliable criterion of origin, 
have been produced under similar conditions to cannels. It is uni- 
versally admitted that cannel coals are of lacustrine origin and owe 
