172 . III. DIST. CHAR. Soil. 



A fissure (Jissura) may be defined, a partial 

 and, generally, superficial rift, mostly of a determi- 

 nate extent in width and length, and, in depth, 

 rarely extending through more than one stratum f. 



A vein (vena) is a rift of a determinate width, 

 but indefinitely extended in depth, and sometimes 

 in length f f f 



f External rifts, or fissures, are generally frequent in limestone 

 rocks, and are sometimes (in Derbyshire at least) filled with mi- 

 neral deposits of ore, c. like the regular, continued rift, or 

 vein. 



ft Veins may be divided into Rake and Pipe veins to which 

 miners add flat works; but these are merely strata, or beds, 

 .worked for the ore which they contain. 



Rake veins are rifts intersecting the strata (never parallel with 

 them) or mass ; of a determinate width, but indefinitely extended 

 in depth and length. Under the Rake vein, generally worked for 

 metallic substances, may be ranked the faults, or troubles, as 

 they are called, in coal soils, whether dykes, gashes, or slips. 

 These are all real veins (though not often worked as such) filled 

 with mineral substances, distinct from the divided rock. It may 

 not be improper to observe, that the term slip, used by miners, 

 does not properly denote the vein itself, but the sudden alteration, 

 which sometimes takes place in the relative height or position of 

 the strata which the vein intersects. This is most remarkable, or 

 rather has been chiefly attended to, in coal countries ; where the 

 strata, on one side a vein (here called a dyke, gash, <5fc.) are 

 generally found higher or lower than the continuation of the same 

 strata on the opposite side of the vein. This shifting or heaving 

 of the beds sometimes takes place, where there is no absolute in- 

 terval or vein formed ; the ends or edges of the dislocated beds 

 still remaining contiguous or, in other words, the rift, en which 



