434 



W. F. Hillebrand — Analyses of three 



The objection to the explanation does not seem to me to be 

 in its inherent improbability, for I believe that every step in 

 the process may And its homologne in the present stage of 

 other regions of similar structure but less age. The objection 

 lies rather in a difficulty not yet named ; namely in the occur- 

 rence of a strong fault or series of faults, by which the eastern 

 margin of the formation is determined, and whose upthrow is 

 on the east. The drainage from the centripetal slopes of the 

 Triassic half-boat must have surmounted this barrier in order 

 to flow to Saybrook, and in doing so may have formed a large 

 lake in the bottom of the boat, to be drained later on when the 

 outlet was deepened. Whether suppositions so transcendental 

 as these shall be approved remains to be seen. 



Cambridge, Mass., February, 1889. 



Aet. XLIV. — Analyses of three Descloizites from nev) 

 Localities ; by W. F. Hillebrand. 



[Read before the Colorado Scientific Society, Mar. 4tb, 1889.] 



1. Mayflower Mine, Bald Mountain Mining District, Beaver- 

 head County, Montana. 



Through Messrs. W. H. Beck and George E. Lemon of 

 "Washington, D. C, was received about a year ago for exam- 

 ination a large lump of friable, uncrystallized material, having 

 a dull yellow to pale orange color, and consisting chiefly of a 

 vanadate, but carrying a large percentage of gangue. Two 

 samples as pure as could be selected from different parts of the 

 lump were analyzed with the following results : 



Molecular ratios. 





I. 



II. 



PbO . 



5602 



55-84 



CuO . 



1-16 



1-13 



FeO . 



0-70 



0-70 



ZnO. 



... 1596 



15-91 



V 2 s 



. 



20-80 



As.O e 



0-32 





P 2 5 . 



0-27 







H s . 



4-37 



4-36 



Si0 2 . 



0-20 



0-16 



CaO . 



o-io 





MgO. 



0-06 







•93 

 •15 



•70 

 ■94 

 •80 

 •32 

 •27 

 •37 

 •18 

 •10 

 •06 



•2508"] 



' 0145 i-4718 

 •0097 \ 4718 



•1968 J 



•1140") 



•0014 J.-1173 



•0019J 



•2428 



4-02 



1-00 



207 



99-82 



From I 27*62 per cent of gangue insoluble in cold dilute 

 nitric acid has been deducted, and from II 22 '20 per cent ; 

 manganese was present in the gangue in small quantity, appar- 

 ently as pyrolusite, but it was not dissolved by the acid. The 

 insoluble portion was found also to retain very small quantities 



