512 Dr. Mac Culloch 07i Vegetable remains 



examination will always detect in these the vegetable disposition, 

 and the sections of the stone will, by cutting through the branches 

 in various oblique directions, lay bare the true structure and dis- 

 tinguish the plant from its adventitious and metallic covering. 



A third, and the most common source of deception and obscurity, 

 will be found in the whimsical and fibrous disposition occasionally 

 assumed by chlorite, its colour often imitating the natural hue of a 

 plant as perfectly as its fibrous and ramified appearance does the 

 disposition and form of one. It is by this substance particularly 

 that appearances strongly resembling confervas are produced, and 

 nothing but a very accurate investigation, with considerable ex- 

 perience in the various forms which this substance puts on, as 

 well as with the aspect and characters of the plants imitated, is 

 sufficient to enable us to distinguish them. In many cases even 

 the most scrupulous attention will fail, a fact which need excite no 

 surprize when it is considered with what difficulty the examination 

 must often be conducted, from a deficiency of light when trans- 

 mitted through these stones, and from the impossibility of bringing 

 into view any considerable portion of the imbedded substance. 

 Here we must have recourse to the chemical means which I shall 

 presently describe. 



It is I believe from the deception to which those specimens have 

 exposed mineralogists, that so much incredulity on the subject 

 exists, every green fibre having been supposed to be chlorite, be- 

 cause it was apparent that chlorite sometimes assumed the form of 

 green fibres. However difficult the distinction, it will be found real, 

 and with sufficient care, generally practicable. The subjoined draw- 

 ings contain representations of some specimens which are undoubt- 

 e<lly chlorite, and of others which present a very suspicious aspect. 

 Among them however will be found some exhibiting an organization 



