4 Johnson and Warren — Geology of Mhode Island. 



of 1873 and reproduced with slight changes by Mr. Holley in 

 1879 in the Transactions of the American Institute of Mining 

 Engineers. He also gives figures for phosphorus, total iron, 

 and silica, as determined at the laboratory of the Bethlehem 

 Steel works. 



The first good description of the cumberlandite was made 

 by Professor M. E. Wadsworth in 1881. He gives its micro- 

 scopical characteristics for the first time, describing it as a rock 

 composed essentially of olivine, or its alteration products, and 

 titaniferous magnetite, containing locally porphyritieally-devel- 

 oped feldspar as an abnormal constituent. He concludes that 

 it is a basic eruptive rock. A short historical account of the 

 hill accompanies the description. 



In 1881, J. D. Dana, reviewing Wadswprtlrs paper, con- 

 cludes that the " Rhode Island magnetite is also of metam or- 

 pine origin," basing his conclusion partly on Wadsworth's 

 statement that the nearest rock is a mica schist some hundreds 

 of feet distant, and partly on a comparison of the occurrence 

 with those of certain New Jersey magnetite deposits to which 

 a metamorphic origin was assigned by Professor C. H. Cook. 



In 1884 Wadsworth published his " Lithological Studies," 

 etc., and in them he devotes considerable space to the macro- 

 and microscopic description of the rock. He classes it as a 

 " Terrestrial Pallasite," viz., a rock possessing a texture similar 

 to the meteorites and composed of a sporge-like matrix of native 

 iron, pvrihotite, or their secondary products such as magnetite, 

 enclosing olivine with or without other accessory minerals. 

 He expresses the belief that the matrix, in the present case 

 magnetite, will be found to pass in depth into the unoxidized 

 metallic iron. He proposed the name Cumberlandite for this 

 and closely similar rocks. The altered types of the cumber- 

 landite are described in some detail in this paper as well as the 

 feldspathic, original type. He seems here to have looked upon 

 the feldspar as an abnormal constituent of the rock. In an 

 appendix he gives a tabulated list of the existing analyses, but 

 makes no particular use of them, doubtless recognizing their 

 poor character. Dr. Wadsworth seems later to have become 

 aware of the original role of the feldspar in the rock and its 

 subsequent replacement by alteration products, for in 1889 he 

 writes of it, — " a rock composed of a spongiform mass of titan- 

 iferous magnetite, containing abundant olivine and more or 

 less feldspar. This is the ore in its unchanged condition as 

 found on one side of the hill, but it passes into more altered 

 forms on the top and other side. In the altered forms the feld- 

 spar and olivine are changed to serpentine, actinolite, and even 

 into talc and dolomite, while the magnetite is diminished in 

 quantity. In the hand' specimens the least altered condition 



