66 Professor Harkness on Coal. 
the mineralogical character of the adjoining rock is perhaps 
still more intimately connected with the richness of the lode 
in ore. This may be owing to very different causes. But 
there are two circumstances which may throw some light 
upon the subject—(1.) Certain beds of the adjoining rock 
are metalliferous, e.g., the Fallbander of Konigsberg, the 
Riicken of the cupreous slate, &c., and substances may have 
been introduced from them into the veins. (2.) Some lodes 
appear particularly rich in ore where they cut certain rocks, 
é.g., argentiferous-quartz formation in gneiss and mica-slate 
of different aspect in the Freiberg district, and various mica- 
slates in the Johanngeorgenstadt district, lodes in limestone 
and lodestone in England. There would appear to have been 
a kind of attraction exercised by certain rocks. The collec- 
tion of facts of this kind should be attended to as it has a 
practical value for miners. Ina scientific point of view, like- 
wise, it appears to indicate that there may be peculiarities 
in districts containing ore lodes which have not yet been re- 
duced to general rules. 
In conclusion, Professor Breithaupt remarks that he con- 
siders it in the highest degree probable that electro-mag- 
netic and other molecular agencies have been concerned in 
the deposition and arrangement of minerals in lodes, but 
in the absence of the necessary data, it is at. present impos- 
sible to say to what extent this may have been the case, 
whether generally or only in particular instances. 
B. H. PAUL. 
On Coal—The Nature of the Plants forming Coal—The 
changes produced by Chemical Action and Compression— 
Associated Mineral Matter—Origin of Coal. By Pro- 
fessor HARKNESS, Queen’s College, Cork. “% 
In order that an idea be arrived at concerning the nature and 
origin of the substance which forms the great mass of our fossil fuel, 
it is necessary that such a definition of this substance be given as 
shall, as far as possible, embrace all the circumstances and conditions 
under which coal presents itself, and also such as should give some 
idea as to the nature of the substance itself. Such a definition may 
describe coal as being chemically altered and compressed vegetable 
matter, associated with more or less of earthy substances, and capable 
