COAL. 305 



importance, and as we have no reason, from our 

 knowledge of the other strata, to expect one so singu- 

 lar. We might therefore extend the general analogy, 

 and expect to find the same series, if it should oc- 

 cur widely, following the lowest red sandstone, or 

 at least inferior to the newer one, or to the saliferous 

 strata. But ignorant as we are of the earth at large,* 

 and uncertain whether its greater revolutions have 

 been all simultaneous and general, it might be dan- 

 gerous to make such a rule exclusive. Thus we must 

 be content to wait for further information ; and at 

 least till geologists have learnt to distinguish more 

 accurately among the secondary strata, and to give 

 their true places to all those deposits of coal which oc- 

 cur above the saliferous sandstone, here separated 

 from the present series. I must only remark, that as 

 the inferior strata are sometimes absent, and as the su- 

 perior ones are often similarly wanting where coal 

 occurs, this series may still essentially correspond, in 

 other countries, with that of Britain, even where the 

 same exact order does not take place. It must remain 

 for geologists to extend their examinations far more 

 accurately and widely, before a satisfactory account of 

 the subject, thus imperfectly sketched, can be produced. 

 In an economical light, founded on this view of 

 the coal series, it is now proper to observe, that it 

 must be fruitless to search for coal below the old red 

 sandstone, and, generally speaking, beneath the moun- 

 tain limestone ; as, to mine after primary coal would 

 be a wild project. It is almost equally useless to seek 

 for it in those strata. It is also unadvisable to at- 

 tempt it, even in countries displaying the upper secon- 

 dary strata at the surface, where indications of coal 

 do not exist ; as it can rarely be known what the 

 superincumbent depth is, or whether, even if that were 



VOL. II. X 



