93 



TAB. CXLIX. 



ARGILLA marga. 

 Argillaceous Marie. 



Class 2. Earths. Order 2. Compound. 

 Gen. 1. Argilla. Spec. 1. Marie. 



Div. 1. Imitative. 



Syn. Tophus turbinatus. Linn. Syst. Nat. ed. 1: 

 v. 3. 190. 



We so frequently find the figure of Corallines, or other 

 organized substances, that we are often puzzled to ac- 

 count for them ; some however are readily understood to be 

 infiltrations taking place of them, and that before us has 

 hitherto been considered by many in this light. The sin- 

 gular regularity of the specimen here figured has given rise 

 to many conjectures. In giving my opinion I desire to 

 discover the truth ; and having made many comparisons, I 

 agree with Linnaeus, that it is rather a Stalactite formed 

 under certain circumstances among other operations of 

 nature, which may be continued to a great extent. Thus, 

 Mr. Martyn observes that a very large space in Derbyshire 

 is of this formation. It is finely undulated : in other re- 

 spects the cones run into each other, something like a 

 child's horn gig — which will separate into a number of 

 cones, more or less perfect, if placed by the fire. From the 

 present specimen I separated some cones, by alternately 

 wetting and drying it. We do not know how minutely 



