Human Foot-Prints i?t Solid Limestone. 21 



The whole Peritremital series is a remarkably pure variety of 

 limestone. A quantitative analysis of a portion of the slab in 

 which the foot-prints occur, gave the following result : 



Carbonic acid, 40.80 grains. 



Lime, 48.80 



Magne^a, . . . . . . .2.60 



Sihca,'' 2.00 



Oxide of iron and loss, .... 5.80 



100.00 grs. 

 Specific gravity, ..... 2.67 



The color of the slab has not been quite correctly given by 

 Schoolcraft. He describes it as of a " grayish blue tint ;" but, 

 on the exposed and worn surface, it has rather a pnrple tint ; and, 

 when fractured, is of a very hght gray. I mention this because 

 the blue tint is by no means characteristic of this group of lime- 

 stones, but is peculiar to the lowest limestones of the Ohio valley, 

 considered the equivalent of the lower Silurian rocks of Murchison, 

 and the Salmon river and Trenton rocks of New York, and on 

 account of this prevaiUng tint, frequently described as the "6/t<e 

 fossiliferous limestones." They lie from eight hundred to one 

 thousand feet lower in the geological series than the Pentremital 

 limestones now under consideration. 



So much for the age of the rock in which these foot-prints are 

 found. The question next presents itself, are they true fossils, 

 or are they the work of art ? 



To aid in the solution of this question, I have given (in the 

 plate accompanying this article) a correct representation of the 

 slab, with the foot-prints and other marks, as they at present ap- 

 pear. That during the twenty two years since it has been quar- 

 ried, no material or appreciable alteration seems to have occurred,* 



* Nor does it appear that these impressions had changed in appearance while 

 the rock was in situ. I quote from the letter of Col. Benton (an eye witness) to 

 Mr. Schoofcraft, referred to in the extracts hereinafter given from the latter gen- 

 tleman's article : 



" The prints were seen when the country was first settled, and had the same 

 appearance then as now. No tradition can tell any thing about them. They look 

 as old as the rock ; they have the same fine polish which the attrition of the sand 

 and water have made upon the rest of the rock exposed to their action. I have 

 examined them often with great attention. They are not handsome, but exqui- 

 sitely natural both in form and position ; square toed, of course anterior to the use 

 of narrow shoes." 



