416 M. Muller on Substances inclosed in Mochastones. 



§ 2. History. 



As far as I know, this matter was first noticed by Blumenbach 

 in his ' Specimen archseologise telluris terrarumque impr. Han- 

 nov. ser. Goetting. 1813/ in which he pointed out the organic 

 nature of the so-called Dendrites, and even recognised amongst 

 them genera which exist at the present day. 



At a later period the subject was considered worthy of especial 

 notice by Macculloch, who however laboured only to prove again 

 their organic nature (Transact, of the Geolog. Soc. of London, 

 ii. 510; Leonh. Taschenb. f. Mineral, xiii. 595*). 



In this state the matter rested, and we merely find it men- 

 tioned occasionally in introductions to geology under the head 

 Chalcedony. 



§ 3. On their Organic Nature. 



This question springs in part from the scarcity of the substance 

 which gives rise to it, which is found only here and there in col- 

 lections of minerals, and then preserved merely as a curiosity; in 

 part, from the prevailing doubt as to their vegetable origin. 



People are easily induced to consider them as dendritic growths 

 of metallic substances, as indeed has been done by many mine- 

 ralogists and botanists ; but I have never heard of an explanation 

 how such growths take place. 



I must indeed add, that amongst these inclosed bodies others 

 are found whose organic origin cannot be denied, though I have 

 never found the former with such a form or texture under the 

 microscope, without whose help no judgement can be formed. 



While some allow their organic nature, we hear others too fre- 

 quently speak of them as belonging to the category of sports of 

 nature. But, it may be asked, what is a sport of nature ? The 

 dendritic formations in marly slate are brought forward as proofs 

 of the existence of fortuitous forms in nature. How far they are 

 related to the bodies in question I cannot say, not having paid 

 especial attention to them. 



Even they however depend on fixed laws, under whose activity 

 they are produced, since their forms so constantly recur. 



But how is it possible in the remotest degree to speak here of 

 sports of nature, when so many forms so frequently recur in these 

 inclosed bodies ? 



To prove their vegetable nature without the help of the micro- 

 scope, Macculloch advised treating them with sulphuric acid, which 

 turned them black. This method should seem however to be less 

 practical than it appears at first, for many inorganic inclosed sub- 



* It is to be regretted that M. Muller had no opportunity of seeing Mr. 

 Bowerbank's admirable memoir, who however appears to have observed no- 

 thing which he considered as referable to the vegetable kingdom. — M. J. B. 



