THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Akt. I. — Contributions to the Geology of Rhode Island: 

 I. Notes on the History and Geology of Iron Mine Hill, 

 Cumberland ; by B. L. Johnson. II. The Petrography 

 and Mineralogy of Iron Mine Hill, Cumberland ; by 

 C. H. Waeeen. 



Introduction. — During the spring of 1905, one of the 

 authors (Johnson) made a geological study of the occurrence 

 of the ultra-basic, titaniferous rock, familiar to petrographers, 

 from the publications of Professor M. E. Wadsworth, under 

 the name of cumberlandite. A geological map of the region 

 and a brief petrographical study of the surrounding rocks as 

 well as of the cumberlandite itself was made. The results of 

 this work were presented as a graduating thesis in the geolog- 

 ical option of the course in Mining Engineering at the Massa- 

 chusetts Institute of Technology. 



In comparing the results with those of other observers in 

 the field, it was found that a fuller knowledge of the relations 

 existing between the cumberlandite and the surrounding for- 

 mations had been secured, and it was deemed desirable to place 

 these on record. It was also noted that no satisfactory chem- 

 ical analysis of the cumberlandite had ever been made, and 

 that consequently the existing petrographical descriptions are 

 all inadequate for so interesting and unusual a rock. Accord- 

 ingly, a rather complete penological study of the rock and its 

 altered forms has been made by one of the authors (Warren), 

 the results of which are also presented in the following pages. 



Am. Jour. Sci. — Fourth Series, Vol. XXV, No. 145. — January, 1908. 



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