Miss M. C. Stopes—On Concretionary Nodutes. 107 
considerable interest to geologists, and also to palzeobotanists from the: 
fact that they contain ‘‘ matted fragments of woody and foliaceous 
material.”” They were made the subject of some comparisons with 
the calcareous concretions from the Lancashire Coal-measures, and as. 
a result certain general considerations were brought forward, which 
call for comment, and which are of sufficient importance to receive: 
attention. 
In the first place, the comparison which Mr. Chapman made 
between the Yarra concretions and the English ‘ coal-balls’ is hardly 
justified by the facts when they are carefully considered. By those 
who have a practical acquaintance with the English Coal-measures 
the ‘ coal-balls’ or calcareous concretions which are found actually 77. 
the coal itself are at once recognised as being very different in their 
nature, formation, and occurrence from the clay ironstone or clay 
nodules which are found widely distributed in the various beds of the 
Carboniferous, and which also contain fragments of plants in many 
cases. Yet, though it is with the latter that the Yarra concretions. 
more nearly approximate, it is to the former that Mr. Chapman has 
compared them. Nevertheless, he calls them ‘clay nodules,’ and 
describes the clayey nature of their outer layers, and states that under 
microscopic examination the matrix ‘‘was seen to consist of quartz- 
grains, fine calcareous and argillaceous particles, brown woody tissue, 
‘and valves of the marine diatom Actinocyclus.”’ Further, the residue 
from the nodule was shown, after treatment with H Cl, to consist of 
‘‘a fine angular quartz sand, the grains of which have a diameter 
varying generally between -l1mm. and ‘018mm. Some tourmaline 
and zircon crystals were also present.’’ None of which things, to my 
knowledge (except the woody tissue and the calcareous matter), are 
in the least characteristic of the true ‘ coal-balls,’ which are singularly 
free from such materials. Of the coal-balls I have examined many 
hundreds, both i si¢%z and in the laboratory, and have also followed 
the results of the many analyses which have been done for the special 
work I have been undertaking. 
Mr. Chapman continues :—‘‘ From the occurrence of the nodules on 
the sides of the old river channel, and seated in depressions, we may 
reasonably assume that they received their form in ‘kettles’ or 
‘potholes’ in the clay bottom of the river bed.” ‘These facts, again, 
are fundamentally ‘opposed to those that hold for the Yorkshire and. 
Lancashire ‘ coal-balls,’? which occur neither in old river channels nor 
in ‘ kettle’ depressions, but are found in a normal seam replacing the 
coal in local patches, in which the stratification of the coal round them 
is regular and undisturbed, and shows none of the ‘swirling eddies’ 
suggested by Mr. Chapman for the cause of the rounded form of these 
concretions. When Mr. Chapman enters into the theory of their 
mode of formation he reveals that he is seriously hampered in this. 
attempt by want of facts and an intimate knowledge of the actual 
details of the case of the Lancashire and Yorkshire ‘ coal-balls.’ 
Though superficially the Yarra concretions and those of the English 
coal-seams may appear to be similar structures, yet I think that. 
enough has been said to show that they are of fundamentally different. 
construction and mode of origin. 
