Mr. With am' s Descriptmi of a Fossil Tree. 299 



deposits we are enabled, by certain species of shells, which are embed- 

 ded in them, to ascertain their precise geological nature (as, for exam- 

 ple, in the case of the Oolitic formation of Brora in Sutherland, resting 

 upon Red Granite), so may we now, I hope, by the obvious distinction 

 between these Fossil plants, possessing distinct structure, be enabled, 

 at once, to ascertain the group of rocks to which they belong. Should 

 similar analysis be taken of the Fossil vegetables possessing structure 

 in other Coal-fields and Mountain Limestone groups, and the results 

 prove equally satisfactory, a new light will beam upon the bewildered 

 miner, and large sums of money be saved to the owners of such sedi- 

 mentary deposits. The following is the analysis of the Craigleith Fossil 

 above described. 



Specific gravity, 2.87 



Carbonate of Lime, 62perct. 



Carbonate of Iron 33 ditto. 



Carbon, 6 ditto. 



100 



Analysis of the Craigleith Tree found in 1826. 



Carbonate of Lime, 60 per ct. 



Oxide of Iron, 18 ditto. 



Alumine, 10 ditto. 



Carbon, 9 ditto. 



Lose, 3 



.100 

 Analysis of the fragment and branch found in Craigleith in 1831. 



Lime, 37.5 



Peroxide of Iron, 24.2 



Coal 38.1 



99.8 



Dr. Gregory, who has been kind enough to examine the abovenamed 

 Fossil, has favoured me with the following remarks upon it : — " The 

 Iron does not exist in the state of peroxide in the mineral. If reduced to 

 protoxide, it would amount to 21.8 p. c, and the loss would be 2.4 p. c. 

 of which a part is water. The Coaly matter is, like ordinary Coal, 



VOL. I. s s 



