FRAGMENT OF SILICIFIED WOOD. 



Jid 



by a volcanic eruption, having been previously siiicified by means of 

 heated alkaline Avaters containing silica in solution. This point, how- 

 ever, could only be settled by actual observation on the spot by a 

 competent geologist. As to the age of the siiicified forest of Colorado, 

 we are in possession of no data whereby a positive opinion mio-ht be 

 arrived at. At the present day the great Sequoias are not found east 

 of the Rocky Mountains, though there is ample evidence of their 

 having at a former period enjoyed a much wider extension in space. 

 We may conclude, therefore, with much probability, that the forest 

 is of Post-Tertiary age, probably Post-Pliocene. 



The specimen which forms the immediate object of the present 

 communication is alleged by its discoverer to be one of many similar 

 specimens which were found upon the surface of the ground surround- 

 ing the stump of one of these siiicified trees ; and it demands con- 

 sideration from three points of view : 1, as regards its microscopic 

 structui-e ; 2, as regards its chemical constitution ; and 3, as regards 

 its form. 



1. As regards the intimate structure of the specimen, we have 

 carefully examined thin sections, ground down on a hone, and soaked 

 either in water or Canada Balsam. These sections show in the 

 clearest and most unmistakable manner the structure of fossil wood, 

 exhibiting woody fibres and medullary rays, and closely resembling 

 some of the specimens figured in Goeppei't's " Monograph of the 

 Fossil Coniferae." We were for some time ixnable to determine the 

 existence of discs upon any of the ligneous vessels. The examination, 

 however, of a section which had been soaked for a long time in Canada 

 Balsam, revealed the presence of these discs on some of the vessels.. 



