520 Dr. Mac CuLLOCH 0/7 Vegetable remalm 



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 po- 

 lished ones all possibility of the adhesion of the lapidary's oil, a cir- 

 cumstance 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 o]>ject 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 containcarbonat 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, Hopfner, and 

 other chemists throw no great light. 



It would be a waste of time to attempt a description of the charac- 

 ter of each individual stone which is found to contain a vegetable 

 substance. However desirable it might be to find a specimen at- 

 tached to its native place of growth, it has not, as I have before re- 

 marked, 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 //; situ. 

 Many of the specimens, and among others those which contain t he 



