Mr. Witham's Description of a Fossil Tree. 301 



wood. Under the microscope, the more compact part, portions of 

 which occur here and there of considerable size, is seen to be composed 

 of similar crystals, embedded in a brown amorphous substance. This 

 brown substance prevails more in some parts of the Fossil than in 

 others ; a difference due probably to the manner in which the decay of 

 the wood took place — but shewing that any two portions of the Fossil 

 mass, taken without selection, must vary considerably in composition. 

 With acids this solid portion exhibits no effervescence, nor is it dissolved 

 by long digestion ; the Lime only, and a small quantity of Iron, are ta- 

 ken up by this treatment. Reduced to a state of coarse powder, which 

 contained necessaiily many fragments of the crystallized Quartz, a por- 

 tion of the Wideopen Fossil gave one per cent, and of the High 

 Heworth Fossil one-half per cent, of Carbonate of Lime. The rest con- 

 sisted of Silica, a variable portion of Alumine, and two or three per cent., 

 probably, of peroxide of Iron. As the whole Fossil is a mixture, only, of 

 these different substances, of which Silica is the predominating ingre- 

 dient, forming, perhaps, four-fifths of the entire mass ; and as it would 

 be nearly impossible to obtain any part of the compound or amorphous 

 portion free from crystallized Quartz, any analytical attempt to estimate 

 the relative proportions of these ingredients would be useful only in 

 regard to the fragment actually reduced to powder and analyzed ; any 

 other portion would be likely to give very different results. I have, 

 therefore, considered it sufficient to determine that the Lime forms a 

 very small, and the Siliceous matter a very great, proportion of the 

 whole substance." 



Here, then, we have strong and distinctive marks of differences be- 

 tween the plants found in the Coal-field, and those which occur in such 

 abundance in the deposits immediately below it. 



In conclusion, I beg to add, we have in this striking and stupendous 

 relic of ages long gone by, an additional proof, amongst many others 

 lately advanced, that plants belonging to the Gymnospermous-Phanero- 

 gamic class, are much more abundant in these early sedimentary de- 

 posits, than continental writers would lead us to believe. 



