424 SUPERIOR SANDSTONES. 



found on the stems of certain palm trees, and 

 supposed to have been derived from some source 

 of that nature. In some of these instances, the 

 originally vegetable nature of the cause is proved 

 by the existence of a portion of coal in tne con- 

 cretion, occupying the place which the bark must 

 have done in the vegetable. It has even hap- 

 pened in some recent cases, that portions of erect 

 trunks of trees, similarly characterized by the 

 carbonized state of the bark, and by the forms of 

 the roots also, have been founcl in these strata ; 

 the place of the wood being entirely occupied by 

 the sandstone. Remarkable examples of this 

 nature have been lately discovered near Edin- 

 burgh, and at Glasgow. 



Although the colours of the upper sandstones 

 vary, the predominant hue is white. This is 

 sometimes very pure at others tinged with 

 yellow. Occasionally also, they are grey, or 

 mottled and striped, in various ways, with white 

 and yellow, or white arid red, or with more than 

 two of those colours. Those tints are however 

 far less various and remarkable in these than in the 

 red sandsftone. In some rare instances, they are 



