Dr. Mac Culloch on Vegetable remains 511 



been quoted in Dr. Thomson's journal, noticing the same fact, and 

 professing the removal of his former doubts. It will be a sufficient 

 apology for not recalling this notice after having thus discovered 

 that the inquiry had not the merit of novelty, that so many should 

 have overlooked, and so many others refused their assent to a fact 

 of no uncommon occurrence. 



The metallic arborizations emulating the vegetable form which 

 occur in the fissures of many stones, and the similar well-known 

 figures in the chalcedonies distinguished by the name of mochas, 

 with the lively though superficial resemblance they bear to plants, 

 have led to the hasty conclusion that all these appearances were of 

 a metallic nature, and have probably prevented that accurate inves- 

 tigation of them which they deserved. The want of botanical 

 knowledge has perhaps also assisted in concealing from most mine- 

 ralogists their true origin, but I may now hope that the possessors 

 of such specimens will hereafter by a more attentive examination 

 confirm the frequency of an occurrence so interesting. 



Another circumstance has assisted in this case in deceiving mine- 

 ralogists, and that is the obscurity in which the vegetable is often 

 involved either by the accidental mixture of metallic oxides in the 

 same stone, or by the actual investment of the whole plant with a 

 thick crust of carbonat of iron. Many of the specimens, and most 

 commonly those which contain confervse, exhibit at first sight 

 nothing but a confused and entangled fibrous mass of oxide or car- 

 bonat of iron. It requires a patient observation to detect in these 

 the existence of a real vegetable structure contained in the stone,, 

 and modifying the deposition of metallic matter. It will be found 

 in fact that the whole plant is incrusted with the metallic deposit, 

 and that it exhibits only here and there its true nature. An accurate 



