. An introduction to geology : intended to convey a practical knowledge of the science, and comprising the most important recent discoveries, with explanations of the facts and phenomena which serve to confirm or invalidate various geological theories. of limestone which dip all round the hill ccc, butare somewhat flattened at the top; the shale and gritstone surround-ing the lower part of the hill are represented ah. The true structureof the hill has been discovered by recent mining operations; severalvaluable metallic veins have been explored in it, and a gallery hasbeen driven into it, as r
. An introduction to geology : intended to convey a practical knowledge of the science, and comprising the most important recent discoveries, with explanations of the facts and phenomena which serve to confirm or invalidate various geological theories. of limestone which dip all round the hill ccc, butare somewhat flattened at the top; the shale and gritstone surround-ing the lower part of the hill are represented ah. The true structureof the hill has been discovered by recent mining operations; severalvaluable metallic veins have been explored in it, and a gallery hasbeen driven into it, as represented in the figure/. It is obvious thatthis arched structure can be formed only by protrusion, whereas theelevation or inclination of plane strata may have been produced bysubsidence. Now, when we consider their near proximity to bedsof toadstone of igneous formation, we can have litde difficulty in as-signing a cause for this protrusion ; but, fortunately, we are not hereobliged to have recourse to conjecture: in driving the gallery towardsthe centre of the hill, a mass of toadstone was met with (e e,) whichwas not cut through when I visited the place in 1830. The sametoadstone was found by sinking a shaft upon it, as represented in the. CRIGH CLIFF. 97 cut at S. In tliis instance we have the effects of protrusion, and thecause, displayed in the same hill. It is true, the black compacttoadstone had not been reached in 1830, but a great mass of indura-ted green earth, which always accompanies it, and is regarded bythe miners as toadstone, and is called by the same name, had beenpenetrated many yards. It was so hard as to require blasting. Onone side of this hill is what is called a pipe vein or opening betweenthe strata, filled with metallic This is represented in the cut atd; the workings in this vein, have been continued nearly round thehill. Near the top of the hill there are quarries worked, which dis-play the strata rising towards the summit on each side. Havin
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Keywords: ., bookcentury1800, bookidintroduc, booksubjectgeology, bookyear1833
