294 Or ^ r O f*b* Strata. [Book VI. 



F. reprefents the fiflure, by which the ftrata are parted, 

 and which is filled up with extraneous rubbilh, carried 

 in after the ftrata were parted. The black vein of 

 coal on the left fide is found with five other ftrata 

 above it; but being interrupted by the fifiiire F. where 

 it comes out to the day, the ftratum of fand, No. 4, on 

 the right fide, on account of the trapping, is found 

 oppofite to it j thence it is to be collected, that the 

 fourth ftratum below that fand 'will be coal ; and when 

 the angle of the dip is obferved, it may be known 

 where to fink a pit, and where the coal will again ap- 

 pear to the day j provided the figure of the furface 

 of the ground will permit it to fhew itfelf. When 

 I was once at the bottom of a lead mine in Derby- 

 Ihire, a miner informed me, that the veins of the 

 metal always make a greater angle with the horizon 

 than the fides of the mountain do, in which they are 

 found and come out to the day j which was probably 

 occafioned by the defcent of the waters of the flood, 

 tearing away much of the matter from the fummit, and 

 lodging it upon the fides and in the vallies beneath, 

 after the ftrata had received their inclination.' 



With refpect to the more internal parts of the 

 earth, for the reafons affigned in the beginning of this 

 chapter, nothing can be advanced with certainty, and 

 hypothefes cannot be relied on. 



By fome it has been fuppofed, that the center of the 

 earth confifts of fire. Mr. Kirwan, however, has fa- 

 tisfadtorily proved, that the notion of a central fire or 

 heat is void of foundation. Since no authentic obfer- 



and at the top into twigs. But the branches are not continued in 

 a ftrait line: they ftart afrefti, at fome little diltance on one fide, 

 as in fig. 2. that by an intervening boundary the metallic matter 

 might be detained in its defcent, and prevented from finking away 

 to the bottom of the earth. See Mr. Hutchinfon's Obfervations 

 in the year 1706, p. 316, 317. 



vation 



