The Petrified Forest of Arizona. 



57 



to the slow process of fossilization. The water must have 

 contained silica instead of lime, in solution, for the trees are 

 silieified. If the water was heated by reason of its proximity 

 to the volcanoes, may be the fossilization was accelerated. 

 The fossil wood is chalcedony, more or less translucent, and 

 of all shades and colors. No two pieces are shaded alike, and 

 none are banded as agates. The delicacy of the tints is 

 remarkable, and the material is used as a gem and an orna- 

 ment. It would be only fair, therefore, to suppose that 

 heated water aided and accelerated the fossilization. The col- 

 oring matter was probably from iron and copper, as some of 

 the colors are those of gems tinted with copper, but, gener- 

 ally, the coloring is presumed to have the tints of iron. 



During the period of fossilization, the sand in which the 

 trees were embedded was cemented so as to form a hard, com- 

 pact sandstone. Subsequently, through volcanic or earth- 

 quake action, the sandstone was elevated, and the lake or bay 

 was drained. The prostrate trees and parts of trees that had 

 been thus transformed by fossilization, into chalcedony, were 

 held in a matrix of less hardness and more flexibility than 

 the chalcedony. After that time, the trees could not accom- 

 modate themselves to the tremulous motions of the earth- 

 quakes as freely as the sandstone could, and the result was 

 that they were broken into short sections or shaken into 

 pieces while embedded in the matrix. 



Since that time denudation from the ordinary wear and tear 

 of the elements has played an important part in sculpturing 

 and draining the territory. Generally, the sandstone contain- 

 ing the broken trees, which is only a few feet in thickness, 

 constitutes the summit of the outliers, or less than one- 

 twentieth of the country, oyer which the fragments of the 

 trees are distributed. The country is eroded, between the 

 outliers, from twenty to sixty feet, while the tops of the out- 

 liers, if connected, would appear almost one continuous plain. 

 Or, describing the appearance in another way, the surface of 

 the country is rolling, except that it is interrupted here and 

 there with more or less abrupt and irregularly defined out- 

 liers, that indicate about the level of the country before the 

 denudation that has taken place in the present geological age. 

 The chalcedony, being imperishable under the action of the 



