Remarks on Mineralogical Classification. 33 
tirely composed of trilobites or small fossil shells, while 
others, which have been used for the distillation of paraffin 
oil, lie immediately above richly organic limestone beds. 
The classification which would make shale and coal im- 
perceptibly merge into one another, mainly because of a 
chemical similarity, is in my opinion clearly erroneous. 
Might not the organised structure visible in certain rocks 
be employed as a distinctive feature in arranging this order? 
We would have little difficulty in distinguishing two great 
classes of rocks and minerals : Jirst, those indubitably 
showing by the microscope their organic texture ; and, 
secondly, those which, while the}^ do not exhibit microscopic 
structure, yet clearly indicate, by their chemical composi- 
tion, a secondary organic derivation. We might thus create 
one great order, and as important a sub-order. The order 
would include the limestones and the various varieties of 
coal, including peat, anthracite, cannel coal. The sub-order 
would comprise the bitumens, ambers, &c. ; in short, with 
the exception of sulphur, all the genera included in the 
seventh order. The species and varieties of bitumens and 
resins would thus be more easily capable of specific sub- 
division. The animal or vegetable origin of the bitumen 
family might thus be left open, and shales would not be 
confounded with coal. The bringing together of two such 
apparently different bodies as limestone and coal is merely 
a popular objection to our general proposal. By following 
the path of inductive science, light might be obtained on 
many dark questions in petrology. As a sample, the micro- 
scopist now detects bituminous globules in rock crystal ; 
let him apply his art to calc-spar and the conjoined families, 
and what curious resemblances to minerals, from which 
they are apparently very different, may he not discover ? 
We might, too, relegate into a distinct class the Torbane- 
hill mineral, the Albertite of Pictou, and the mineral of St 
John's, N. B., — bituminous substances the true nature of 
which has been the cause of so much discussion amongst 
scientific men. In the opinion of many most competent 
observers, these minerals exhibit no microscopic structure 
similar to coal ; while several able chemists affirm that their 
VOL. III. E 
