. Edinburgh journal of natural history and of the physical sciences . IS not the only substance wliirh is found to contain animal and vogctable wthin Us nodules. Small portions of moss plants, and other ervpto^amia, «re frequently found, beautifully preserved, in the rock crystal, topaz, and ^ate, .11 the mmute lineaments of their original structure. This affords another proof of the iact that such crystals must have been in a fluid state, without any jreat increase of temperature, at the period when they assumed their soHd form. .Many of these stones " well as jaspers c
. Edinburgh journal of natural history and of the physical sciences . IS not the only substance wliirh is found to contain animal and vogctable wthin Us nodules. Small portions of moss plants, and other ervpto^amia, «re frequently found, beautifully preserved, in the rock crystal, topaz, and ^ate, .11 the mmute lineaments of their original structure. This affords another proof of the iact that such crystals must have been in a fluid state, without any jreat increase of temperature, at the period when they assumed their soHd form. .Many of these stones " well as jaspers contain various figures assuming the forms of vegetation ; bein" in i-eality, merely accidental admixtmes of various metalUc substances, which, in crj°tal- lizing, thus assume the appearance of leaves and stems of plants. Of this kind are the mocha stone, arborescent jasper, landscape marble, &c. Drops of water, how- ever, and portions of air, are occasionally found in such crystals, under circumstances which led Dr Davy to suppose that these have been enveloped in the crystal while under great expansion by heat. On carefully opening the cavities, he found that the water and air diminished in volume, when exposed to tlie ordinary pressure of the atmosphere, in some instances to the extent of six to eight times their bulk in the chalcedony to the extent of sixty times their volume.
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Keywords: ., bookcentury1800, bookdecade, bookpublisheredinburgh, bookyear1835
