194 bulletin: museum of comparative zoology. 



This analysis may be compared with those of the ooHtie hematite 

 ore of the CUnton of New York, Usted by Xewland and Hartnagel 

 (Bull. 123, N. Y. state mus., 1908, p. 62). 



1 2 3 4 5 



FeoOs 69.17 42.97 79.98 63.00 71.82 



SiOo 11.57 29.72 9.98 12.63 11.34 



AI263 3.92 4.13 2.4 5.45 3.91 



MnO .19 .37 tr. .15 1.63 



CaO 5.8 8.57 1.54 6.2 3.97 



MgO 2.27 1.96 .3 '2.11 2.21 



S .28 .837 .23 



P2O5 1.726 1.534 1.239 1.5 2.096 



Comparing these analyses, it will be noted that the "linsen" have 

 about the same iron content as some of the Clinton oolites, and about 

 the same amount of clay, manganese, and phosphates, but less silica, 

 lime, and magnesia. The high silica content of the Clinton ore is due 

 to the presence of nuclei of sand in the spherules, whereas the nuclei 

 of the linsen, when such can be observed at all, seem to be calcitic 

 fragments of fossils. 



The linsen have much the same size and shape as the spherules in 

 the oolitic Clinton ore, most of them being from .5 to 1 mm. in diameter, 

 and somewhat flattened or lentil shaped. This flattening, in the case 

 of the Clinton oolites, has been ascribed to pressure, but in the case 

 of the linsen it seems to be the original form, for, while these discs 

 often lie parallel to the bedding, very large numbers of them do not, 

 but are imbedded at all angles. 



The mode of occurrence of these linsen has some bearing upon the 

 rival theories of the origin of the oolitic sedimentary hematite ores. 

 The view put forward by Shaler was that they w^ere replacements of 

 original limestone effected by the circulation of ground water, while 

 C. H. Smyth, Jr., considers these ores to be original sedimentary 

 deposits. The Russian occurrences are explainable only by Professor 

 Smyth's views, since : — 



First; the linsen occur in a limestone which is not otherwise oolitic. 



Second; the linsen occupy definite layers which can be traced 

 laterally some 300 miles through a series of gentle undulations, always 

 maintaining a definite horizon, as shown by evidence of fossils, and 

 without any relation to the present water table. 



Third; the lower linsenschicht passes laterally into a true conglomer- 



