20 NEW YORK STATE MUSEUM 
Landis ** briefly described the methods then employed in operating 
the Tilly Foster mine, but contributed nothing new to the existing 
knowledge of the geology of the deposit. Eight years more elapsed 
before any additional work was done on these ore bodies. Stewart *° 
then attacked the problem in a different way, making use of petro- 
graphic methods in an effort to determine the character and origin 
of the ores. Stewart described two belts of magnetite in Putnam 
county, one lying along Canopus creek, the other lying along Sprout 
brook. The Canopus creek group consisted of the Canada, Sunk, 
Pratt, Sacket, Denny and Nelson mines, and the Sprout brook 
group consisted of the Croft and the Todd mines. Brief petro- 
graphic descriptions of the wall rocks of these mines are given, but 
Stewart was unable to arrive at any satisfactory conclusions as to 
the origin of either the ores or the associated gneisses. He 
apparently favored a sedimentary origin for the Canopus Creek 
group, as he stated (p. 293) that it “has no features that can not be 
accounted for by considering it a metamorphosed bed of magnetite 
sand.” And this, notwithstanding the associated coarse feldspathic 
granite cut by veins of magnetite and marked evidence of syntexis 
immediately adjacent to and connected with the ore bodies! The 
Sprout Brook group, according to Stewart, “suggests replacement of 
a limestone lens, possibly connected with the action of an acid 
intrusive’ (p. 293), but the uncertainty that he felt with regard to 
the genesis of these deposits is expressed as follows: “It seems 
probable that the Precambrian magnetite ores, although resembling 
each other in shape and having in a large way similar associations, 
are of various origins. In a complex series of sediments abundantly 
injected with many kinds of intrusives and afterwards intensely 
metamorphosed, it is but reasonable to suppose that sedimentation, 
segregation, chemical precipitation, replacement and contact action 
have all done, in various places, some work in concentrating so 
widely distributed a metal as iron.”’ (p. 294) 
A short paper by Stoltz * descriptive of the equipment and method 
of operation of the Forest of Dean mine in Orange county, and a 
very creditable paper by Koeberlin * on the region in the vicinity of 
88 Landis, Edward K. The Tilly Foster Mine. The Journal of the Frank- © 
jin Institute, v. CL, p. 223-26. 1900. 
39 Stewart, A. C. The Magnetite Belts of Putnam County, N. Y. The 
School of Mines Quarterly, 29: 283-94. 1008. 
40 Stoltz, G. C. The Forest of Dean Iron Mine, New York. Eng. and 
Min. Jour. 85: 1091-93. 1908. 
41 Koeberlin, F. R. The Brewster Iron-bearing District of New York. 
Economic Geology, 4: 713-54. 1900. 
