. III. DIST. CHAR. Soil. 171 



direction) but of a determinate, and, more or less,, 

 uniform thickness. 



A stratum is said to be regular ( stratum regu- 

 lare) when it is parallel with the accompanying 

 strata, and continues throughout uniform, or nearly 

 so, in its thickness. 



Irregular (stratum irregulare) when it takes a 

 different direction in its dip f &c. from that of the 

 attendant strata ; or when it does not preserve the 

 same thickness through any considerable extent. 



A semistratum f f is a very thin seam or stratum 

 of clay, &c. separating the thicker strata of stone, 

 or other matter, from one another. 



A Rift (Rima] is a cleft or separation in the 

 mass or stratum ; generally filled with mineral sub- 

 stances distinct from that which forms the body of 

 earth or rock intersected The rift, according to 

 its structure, may be denominated a fissure or a vein. 



f In miners' language, when a stratum is not perfectly horizon- 

 tal, its fall or declination is called the dip ; its elevation, the rise ; 

 and the edge of the stratum terminating the rise, is denominated 

 the crop of the bed when this appears at the surface, the stra- 

 tum is said to crop (in Derbyshire basset} out. The bearing of 

 the bed, is that direction, in which a line might be drawn across 

 the surface at right angles with the rise and dip the stretchy or, 

 as it is sometimes called, the course of the stratum, is its furthest 

 observable extent in any direction but, as this is generally on the 

 line of bearing, the terms are often used indiscriminately. 



ft In Derbyshire, called the ivay-board. 



