820 MYRON L. FULLER 



latter was deeply buried or after it had become exposed at the 

 surface through erosion. The extent of some of the etched sur- 

 faces, frequently amounting to several yards, or even rods, and 

 the apparent continuation of these surfaces indefinitely into the 

 rock, though affording no positive evidence, is at least suggest- 

 ive of deep-seated conditions. The evidence afforded by the 

 bowlders, however, appears to be more to the point, for it is dif- 

 ficult to conceive of conditions which would permit solutions to 

 enter such bedding planes and to penetrate and etch the pebbles 

 throughout their extent, while the external portions of the same 

 bowlders, both where exposed to the atmosphere and to the 

 humus of the soil, are entirely without evidences of etching. 



Source and ?iature of the solvent. — The more sandy portions of 

 the conglomerate at Blossburg contain considerable numbers of 

 feldspathic grains, which, on weathering, it may be conceived, 

 might have afforded alkaline solutions of sufficient strength to 

 have produced an etching of the quartz. The fact, however, that 

 other sandstones and conglomerates higher in feldspathic constit- 

 uents in equally advanced stages of alteration, do not, in general, 

 show any evidences of etching, makes it improbable, in the 

 present instance, that the alkaline solutions were the active 

 etching agents. 



There appears to be no reasonable doubt that the solutions, 

 which produced the etching about the fossil vegetable remains, 

 were derived from the vegetable matter itself, in the process of 

 the change from the original woody state to the present car- 

 bonized condition. Vegetable remains are abundant in many 

 parts of the conglomerate, and must have furnished considerable 

 quantities of organic acids. If, in fact, such was the source of 

 the etching solutions, the latter, in order to reach the bedding 

 planes or other passages, must have traversed the mass of the 

 rock, probably through the agency of the force of capillarity. 

 That the portions of the rock thus traversed are lacking in 

 visible etching is probably due to the wide diffusion of the 

 solutions and the relatively immense areas of the surfaces of 

 the constituent grains. 



The evidence, as far as it goes, would appear to favor the 



