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ESSAY VIII.
Dr. Kidd observed one morning a narrowcrevice running along his path. A few daysafterwards he found this crevice widened,and, opening into it on either side, manylateral crevices, which at the further ex-tremity became gradually narrower till theywere lost.
It is probable that fissures in general havebeen produced, as these undoubtedly were,by shrinking, and are coeval with the con-solidation of strata.
A crystal of calcareous spar will breakmost readily in laminae. A broken crystalof quartz will be generally speaking con-choidal, and of corundum ragged; so eachuncrystallized body has a more or lessdeterminate fracture. Blocks of granite7