450 A POPULAR EXPOSITION OF ‘(HE 
beds of rivers, or occupy comparatively low ground. The city of 
Cincinnati is situated in a remarkable valley of this kind. Finally, 
it must be observed, that when strata lie in parallel beds (as in fig. 59), 
LEZ U LL 
the stratification is said to be conformable or concordant. When on 
the other hand, the beds are not parallel, the stratification is said to 
be unconformable. The accompanying section, in which the inclined 
beds belong to the Laurentian, and the 
overlying beds to the Lower Silurian 
series (see Parr V.), as shown on 
Crow Lake, north of Marmora village) 
is an example of unconformable strati- 
fication, or of want of concordance be- 
tween these two series of rocks. As 
explained further on, a want of con- 
formability always indicates a geologi- 
cal break, or the commencement of a new geological period. 
Both horizontal and inclined strata frequently exhibit fractures of 
greater or less extent. Mineral veins, it may be mentioned, consist 
essentially of cracks or fractures running through the surrounding 
rocks, and filled up, by various agencies, with sparry, earthy, and 
metallic matters. The strata on one side of a fracture are often dis- 
placed, being thrown up or down, as it were. This peculiarity is 
technically termed a fault. An example is 
shewn in the annexed diagram. ‘The levels oc- 64 
cupied by a displaced bed are sometimes only a 
few inches, and at other times upwards of a 
thousand feet, apart. At the first formation of 
a fault or slip, an escarpment or terrace of 
greater or less height must necessarily have 
arisen ; but in very few cases (if in any case 
unconnected with existing earthquake pheno- 
mena) is anything of this kind now observable, the ground having 
