24 
* 
It was next shewn that coal altered by contact with 
igneous rocks does not form Anthracite, but cinder coal or 
soot coal. The phenomena observed at the contact of coal- 
seams with the dyke at Cockfell and the basalt of the Eowley 
Hills were minutely described with reference to this point. 
Our almost complete ignorance of pressure as a metamor- 
phic force renders it unsafe to speculate upon its possible 
influence in this case. Some features of the Anthracites of 
the Alps and of the Basse-Loire suggest that decomposition 
of so unstable and complex a substance as coal may be 
facilitated by pressure. 
Summary. 1. That coal loses its volatile constituents by 
simple evaporation at ordinary temperatures. 
2. In this process it loses its cubical fracture. 
3. This process of evaporation is facilitated by disturbance 
of the strata. 
4. There is no evidence to shew that a seam of Anthracite 
has ever resulted from contact with heated rock. 
ON THE STRUCTURE OF GANOID FISHES, INTRODUCTORY TO AN 
ACCOUNT OF THE GANOID FISHES OF THE YORKSHIRE 
COAL-FIELD. BY L. C. MIALL. 
Almost all that is really known about Ganoid Fishes is of 
modern discovery. The year 1844 is the era of sound 
knowledge, the commencement of true progress so far as this 
branch of zoology is concerned. Nothing but descriptions 
of no physiological value, and generalisations attractive in 
manner but devoid of substantial accuracy, can be derived 
from the previous literature of the subject. Even the magni- 
ficent "Poissons Fossiles" of Agassiz does not suffice to 
qualify this statement. We shall see hereafter how sharp a 
line is to be drawn between the already obsolete discussions 
of thirty years ago and the permanently valuable discoveries, 
