Diamonds and precious stones, a popular account of gems .. . Fig. 2.—Horizontal Columnar Basalt at St. Helena. completely different from that of igneous forma-tions, that they may be recognized at a great dis-tance, even by inexperienced eyes. Being depositedin water in parallel layers, they have preserved thesame disposition after being left dry. Sometimes,indeed, the horizontal layers have been singularlydisplaced from their original direction : suddenchanges and movements of the soil have tilted themup and contorted them ; but still the parallelism of 8 PRECIOUS STONES. the strata, and thei
Diamonds and precious stones, a popular account of gems .. . Fig. 2.—Horizontal Columnar Basalt at St. Helena. completely different from that of igneous forma-tions, that they may be recognized at a great dis-tance, even by inexperienced eyes. Being depositedin water in parallel layers, they have preserved thesame disposition after being left dry. Sometimes,indeed, the horizontal layers have been singularlydisplaced from their original direction : suddenchanges and movements of the soil have tilted themup and contorted them ; but still the parallelism of 8 PRECIOUS STONES. the strata, and their disposition by successive layers,is nearly always clearly discernible. Fig. 3 is an. Fig. 3.—Structure of Sedimentary Rocks. example of sedimentary rock, and it shows verydistinctly the regularity of structure which theserocks usually display. Beyond this general distinction there is another, GEOLOGICAL POSITION. less prominent perhaps, but quite as definitelymarked. The remains of myriads of animals and
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectgems, booksubjectprec
