48 



GEOLOGY CONIFEROUS TREES IN VOLCANIC TUFA. 



plants led me to suppose that during the interval between the deposition of the lower and 

 upper of these layers a growth of vegetation had covered the lower stratum, which became 

 enveloped in the sediment which formed the upper. The specimens which I obtained of these 

 vegetable impressions did not permit me to determine the class to which they belonged. The 

 branches are opposite and alternate, and the plant must have somewhat resembled the salicornia 

 which now grows on our salt marshes. It is possible, too, that these stems of plants may have 

 been transported and deposited at the bottom of the water; but the regularity of their arrange 

 ment, and the carbonaceous matter below, indicated to my mind that they had grown where 

 they were found. 



Two or three hundred feet higher up in this series I found the trunks of large coniferous 

 trees, and stems and roots of small plants imbedded in strata somewhat similar to those which 

 I have described ; but in these cases the vegetable matter had not been fossilized, and resembled 

 decayed wood ; the appearance of the trunk set with branches, of which the extremities were 

 broken off, the roots still attached, gave the impression that they had not been transported to 

 any great distance from where they grew. In general form and mode of branching they closely 

 resembled the trees of cedar now growing scattered over the declivities of the canon. 



The succession from the bottom of the canon to the general level of the plateau, together 

 with these, includes a layer of trap, which forms a horizontal stratum twenty or thirty feet in 

 thickness, occupying a place nearer the top than the bottom of the section. 



NORTH BANK OF PSUC-SEE-QUE CREEK. 



On the banks of Mpto-ly-as river, in one locality, was a succession of seven of these layers of 

 trap, as perfectly as the materials with which they were associated, and on the slope of the 



