IN THE RED SANDSTONE OF POTTSVILLE. 7 



I am not disposed to undervalue the difTiculty which exists in dividing the carboniferous 

 system from that whicli immediately underlies it. It is and has been " debateable ground." 

 But in placing these Pottsville "foot-marks" in the "red shale formation, No. 11," 

 and then considering, with many other geologists, that Formation No. 1 1 was the 

 Devonian or upper portion of the Old Red Sandstone, it never occurred to me that 

 the place of these " ancient foot-prints" could be converted into the appearance of a geo- 

 logical error, when I expressly stated they were found near Mount Carbon, in the " red 

 shale Formation, No. 11," of Prof. Rogers. And when he says, that they "are of an 

 age essentially later than that attributed to them," and but a few hundred feet below the 

 conglomerate, (For. 12,) which marks the beginning of the productive coal series, in 

 which similar foot-prints, attributed to batrachian reptiles, have been previously met with 

 in Western Pennsylvania,* an erroneous impression has been made on the minds of 

 geologists, that I had made a mistake in the geological position of the foot-marks, and it 

 is to this point I wish to draw the attention of the geologist, viz., that I gave Prof. Rogers' 

 own nomenclature to the rock, " red shales," (" Formation No. 1 1 ,") and stated it to be about 

 1730 feet below the coal formation, (No. 13,) which Formation according to his measure- 

 ment, was 6750 feet thick at Pottsville. Taking, then, his measurement, I presumed 

 these "foot-marks to be about 8500 feet below the upper part of the coal formation there." 

 The very interesting " foot-marks" discovered by Dr. King, being near to the upper por- 

 tion of the Coal Formation in the vicinity of Greensburg, Penna., are very essentially 

 removed and later, by two Formations, according to the Table of Formations of Prof. 

 Rogers himself, and must therefore carry back the existence of an air-breathing animal, 

 not, as he stated, that " they carry back its age only by a single leaf," but by two Forma- 

 tions, — that is, from Formation No. 13 back to Formation No. 11, leaving the great con- 

 glomerate Formation No. 12, interposing its mass, 1031 feet, and descending below its 

 lower limits 700 feet, into the "red shale," (For. 11.) 



As to the difference of opinion between Prof. Rogers and the able geologists quoted 

 above, regarding this " red shale formation," whether it be the equivalent of a part of the 

 Devonian (upper portion of the Old Red Sandstone,) or not, it is a matter of little moment 

 in this case. That is a question to be definitely settled when we get more palaeontologi- 

 cal evidences, and when we obtain more of the organic remains of this " red shale,'''' 

 (For. 11,) in which I was fortunate enough to have observed the distinct trace of the 

 oldest " air-breathing animal," then known in the sedimentary rocks of the globe. With- 

 out more records of the organisms of existing life at the epoch of this ^^ Red Shale Forma- 

 tion,'''' assured analogies cannot be established; and a difference of opinion may reason- 

 ably exist at the present time, as to the equivalents of the masses in Europe with ours 

 on this side of the Atlantic ; but in the total absence of the Old Red Sandstone I should not 

 concur with Prof. Rogers.t 



* By Dr. King, in Formation 13. 



f In regard to their line of division, Mr. Ilall very judiciously remarks, that the separation between the car- 

 boniferous and lower deposits is far from being well defined, and not as well ascertained as llie separation 

 " between the Devonian and Silurian." (Am. Journal, vol. 7, p. 47.) 



