38 Outlines of Geology. 



swallows up annually considerably more than a million of chaldrons 

 exclusively from the Tine and Wear districts ; it might appear that 

 the apprehensions of some worthy persons upon this score were 

 not altogether without foundation. It is however admitted, on 

 the other hand, that the Newcastle mines only are capable of con- 

 tinuing their supply for another thousand years ; and if this reflec- 

 tion is insufficient to satisfy the disquieted minds of those who 

 are still uneasy, they may console themselves with the reflection 

 that there are many other districts which have only been, as 

 it were, begun upon, and probably numerous deposits of which we 

 are as yet ignorant, but which will be searched for and found 

 when wanted. Besides which, it may, I think, be calculated, that 

 of every chaldron of coals consumed in our ordinary fires, about 

 one-eighth part is lost in the character of soot, smoke, and other 

 unburnt matters; so that in London only, up wards of 100,000 

 chaldrons of coals are thus dissipated and unprofitably applied 

 to the contamination of our atmosphere, which smoke, by 

 improved methods of combustion, might be turned to profitable 

 account. 



In speaking of the general arrangement of the coal strata, I 

 have said nothing of the dislocations to which they are subject, in 

 consequence of what are called troubles, or slips, and dikes ; that 

 is, the strata are cut through, broken off, and sometimes thrown 

 up on one side, and depressed on the other ; and by the fissures 

 and cracks thus produced are filled with broken stones and frag- 

 ments of the strata, or with a hard species of rock called a dike, 

 near which the coal is converted into a cinder, and from its cavi- 

 ties emits those tremendous torrents of inflammable gas, techni- 

 cally called blowers. 



To the probable origin of these faults, or dikes, I shall after- 

 wards advert more at full ; they record one fact, namely, that the 

 coal strata, subsequently to having assumed their present disposi- 

 tion and arrangement, have been subject to various disturbing 

 causes, breaking their continuity merely in some instances, but in 

 others affecting the whole district, and throwing it for hundreds 

 of acres together out of its original position. 



