ON THE BASALTIC COUNTRY IN IRELAND. 173 



Facts applicable to geological Questions. Geological 



1. Every stratum preserves accurately, or very nearly, the The strata uni- 

 same thickness through its whole extent, with very few ex- ^™ m l lc 

 ceptions. 



2. The upper and lower surface of each stratum preserve Both surface* 



ii •• i .i ii ,i parallel, unless 



an exact parallelism, so long as they are covered by another one h as been 



stratum ; but when any stratum becomes the superficial one, exposed to the 

 its upper surface is scolloped, or sloped away irregularly, 

 while the plane forming its bage continues steady, and recti- 

 lineal; but the parallelism of its planes is resumed as soon 

 4s another stratum is placed over it. 



3. The superficial lines bounding the summit of our fa- The line of the 

 cades, and our surface itself, are unconnected with, and un- verned by the 

 affected by, the arrangement of the strata below them. strata below. 



4. Nature, in the formation of her arrangements, has ne- 

 ver acted upon an extensive scale in our basaltic area, (at 

 least on its northern side, where our continuous precipices 



enable us to determine the point with precision,) but changes Materials and 

 her materials, or her arrangement, or both, every two or * rran g en J ent 



, . , . J frequently 



three miles, and otten at much smaller intervals. changed. 



5. AVherever there is a change of material, as from one The changes 

 stratum to another in a vertical line; or where the change is alwayssudden, 

 in a horizontal direction by the introduction of a new system ; 



or where a whyn dike cuts through an accumulation of 

 strata; in all these cases the change is always per saltum and 

 never per gradus, the lines of demarcation always distinct, 

 and well defined; yet the different materials pass into each -without inter- 

 other without interrupting the solidity and continuity of the [jJJulty! C °** 

 whole mass. 



6. The facades on our coast are formed as it were by ver- Precipices. 

 tical planes, cutting down, occasionally, the accumulations 



of our strata; the upper part of these facades is generally 

 perpendicular, the lower steep and precipitous. 



7. The bases of our precipices commonly extend a con- Their base* ex- 

 siderable way into the sea; between the water and the foot tend int0 A* 

 of the precipice, (and especially near the latter) there is 

 frequently exhibited the wildest and most irregular scene of 

 confusion, by caTeless observers supposed to be formed by Apparent fra^ 

 the ruins of the precipice above, which have fallen down; mefttso ° tl,e * 



such. 



