204 T. 8. Hunt—The Decay of Rocks. 
32. Those who have read what I had written on the subject 
previous to 1876, and especially my discussion of the origin of 
these ores in 1874,*’ are aware that I have never advocated any 
suchtheory. I have, it is true, endeavored to find in the insol- 
uble products of decay of these ancient crystalline rocks, the 
source not only of the clays and sands of the succeeding sedi- 
ments, but of their contained iron, whether diffused or accu- 
mulated in ore-masses. ave, however, at the same time, 
garded in seeking the cause which produced these limonites,” 
adds, “in 1888, and independently of Prof. Shepard’s obser- 
vations, Dr. R. S. M. Jackson reported to Prof. H. D. Rogers, 
substantially the same conclusion from the study of the limon- 
ites of Center and Huntingdon counties.” “ é 
38. This same view in fact was well stated by Lesley him- 
self in 1864, when he said “ the brown-hematite ore-deposits 0 
Mount Alto follow the edge of the slates and sandy lime- 
stones,” and are “ but the residues of these beds after decompo- 
sition and dissolution ; the honey-combed and altered edges’ of 
the slates and limestones themselves, “after the lime has been 
washed out of them, and their carbonated and sulphurett 
iron has been hydrated and peroxidized; the slates having 
formed the red and white clays.” He further described at one 
locality of the region in question “an outcrop of almost un: 
changed blue carbonate of iron and lime, several feet thick * 
41 Proc. Amer. Institute Mining Engineers, iii, pp. 418-421. 
* Second Geological Survey of Penn., Report C, p. 143. 
Se 
