58 



FOSSIL PLANTS. 



" It consists of carbonates, soluble and insoluble silicates, quartz, and iron-pyrites. The 

 carbonates are removed by dilute acetic acid, and consist of carbonate of lime, with a very 

 little of carbonate of iron, and carbonate of magnesia. The insoluble silicates consist 

 principally of the silicate of alumina, with a little lime, magnesia, potash, and soda. 

 " Composition of the 'Ash,' after drying it at 212° Fah. : 



a 



at 



CO 



O 00 



— O 



•3 ^ 



<U fa 



'o 



'' Silicic acid 



Ferrous oxide 



Manganese 

 ^ Alumina 



Lime 



Magnesia 

 l^ Carbonic acid 



Insoluble silicates 



Bilsulphide of iron 



Water 



13-20 



18-26 



•78 



8-13 

 13-47 



5-06 



8-40 



28-76 



•70 



3-23 



99-99 



Specific gravity 2*790. 

 Analysis of a stem oi Lepidodendron from the Ash, previously dried at 212° Fah. 



Carbonate of Lime ... 



8916 



Carbonate of Magnesia 



1-26 



Carbonate of Iron 



1-06 



Carbonate of Manganese 



2-22 



Ferric Oxide ... 



1-39 



Insoluble matter 



2-24 



Carbon 



2-44 



99-77 



Specific gravity 2 611." 



The analysis of this fossil plant shows apparently that the decomposing wood had the 

 power of attracting the carbonate of lime from the surrounding matrix in which it was 

 imbedded. 



Both the form and the structure of the fossil plants in the ash have been beautifully 

 preserved. They remind us much of the plants found in the Coal-measures of Lancashire, 

 so far as their genera and species are concerned. From the appearances which they now 

 present, we see they were growing in water, on the spots where they are now found, when 

 fine ash, erupted from a neighbouring volcano, quietly and gradually enveloped them in the 

 matrix in which they occur. We find the fragile leaves of the most delicate Sphenopteris, 

 and the fine-pointed leaves of Lepidodendron, just as they grew, without the slightest 

 fracture or disarrangement. Nearly all the stems appear to have suffered little from 

 compression or disturbance in their parts. (See notices of this trappean ash interstratified 



