PETRIFIED FOREST OF MISSISSIPPI 



469 



sion has extended several Act into tlie 'J'ertiary. There are at least ten 

 logs exposed in this amphitheater whieli vary considerahly in color and 

 composition. Some of them arc almost pure white and apparently con- 

 tain nearly puie silica; others are stained with more or less of foreign 

 matter. 



IMiese logs vary in size and preservation and none of them piesents 

 the full length of the original tree. The largest observed is about six 

 feet in diameter by twenty feet in length and is of a brown color. 



Fig. 5. 



Petkified Log from Pittsboeo, Miss., now on the lawn of Dr. Calvin S. 

 Brown at the University of Mississippi. 



Another is four feet at base by about seventeen feet in length. A dark- 

 colored log near by is five feet at base and eleven feet long. Another in 

 a ravine to the east is four feet by twenty feet ; and there are still other 

 logs and fragments of logs scattered at various points. 



Most of these logs now^ rest upon the Tertiary formation and there- 

 fore are slightly displaced ; that is to say, the sand of the Lafayette for- 

 mation has washed from beneath them and left them lying ui)on the 

 Tertiary. In several places however in the vertical erosion walls logs are 

 seen projecting from the Lafayette sand some distance above the 

 Tertiary. 



In the accompanying illustration, number four, the line of union 

 between the Quaternary and the Tertiary is distinctly seen running hori- 

 zontally through the middle of the picture. Some distance above this 



