32 Proceedings of the Royal Physical Society. 



And if our ideas of a mineral species be thus overturned, 

 so will the consequent classification into orders and genera. 

 In the re-arrangement of our mineral orders, it maybe found 

 expedient to include their derivative rocks. Thus, observers 

 may afterwards find that peculiar minerals characterise cer- 

 tain classes of volcanic rocks, whilst the metamorphic rocks 

 are the special habitat of others, and the sedimentary or 

 organic of yet different varieties. This would thus involve, 

 that our treatises on mineralogy contain likewise much more 

 of petrology than they ever have done. 



The examination of what is given in our mineralogical 

 treatises as the seventh order, the Inflammables, will show 

 how artificial our present classification is. In it we have 

 sulphur, coal, the resins, the inflammable salts, minerals no 

 doubt possessing one physical character in common, but 

 differing wide as the poles asunder in their other characters. 

 Nor are the subdivisions of the order more satisfactory, as 

 is well known from the repeated recurrence in our legal 

 courts of the question, "What is coal?" Chemistry has been 

 mainly relied on in considering this query. But a little 

 study of the order will convince us that the foundations on 

 which we build our individual discriminations of the various 

 minerals must be physical and not chemical. A close 

 chemical analogy subsists betwixt minerals of the order 

 otherwise manifestly of very different properties. Thus, 

 certain varieties of bitumen and cannel coal are nearly 

 identical in chemical composition. Again, peat, coal, the 

 bitumens, the ambers, are all under the same chemical cate- 

 gory. But reasoning based on such an analogy may lead us 

 into serious practical mistakes. Thus it has been generally 

 assumed that bitumen and coal were of vegetable origin. 

 Now, it has been indisputably proved that the petroleum of 

 Canada is of animal origin — the animal remains of the coral 

 builders of the Silurian and Old Eed Sandstone reefs of the 

 American continent yielding the material whence it is 

 derived. Again, many shales must have obtained their 

 bituminous character from animal remains, as is shown both 

 by their imbedded fossils and their juxtaposition with lime- 

 stone beds, richly fossiliferous. Some shale beds are en- 



