Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/530

520 possess the first of these properties, and that neither of these effects resulted from thus treating common chalcedony. Previously to these trials the precaution was also taken of boiling the specimens for a considerable time in a solution of pure potash, to remove in the polished ones all possibility of the adhesion of the lapidary's oil, a circumstance which would inevitably have led to fallacious results. In these experiments ample confirmation appeared of the deductions which had been made from botanical examination, and I was further enabled to detect many specimens of chlorite, where I had not suspected its existence. The same trials afforded a test which I found in many instances to be very easily applicable to the object of this distinction. This test consisted in the effervescence which is produced when boiling sulphuric acid is applied to those chalcedonies which contain chlorite, while those which contain vegetable fibres blacken the same substance without exciting effervescence. I need scarcely add that I laid no stress on the method of distillation when the stone appeared to contain carbonat of iron. It was not necessary to examine into the cause of the effervescence produced by the action of the sulphuric acid on the chlorite, a circumstance on which the very uncertain and contradictory analyses of Meyer, Höpfner, and other chemists throw no great light.

It would be a waste of time to attempt a description of the character of each individual stone which is found to contain a vegetable substance. However desirable it might be to find a specimen attached to its native place of growth, it has not, as I have before remarked, yet occurred to me, nor do I find that it has occurred to any of those who have noticed the same facts. Yet the appearance of many of the chalcedonies which contain well ascertained specimens of plants, is such as to render it likely that they do now occur in situ. Many of the specimens, and among others those which contain the