F. Waldo — Bruckner* s Klimaschwanlcungen. 141 



of which scheelite is the type. If the natural molybdate and 

 tungstate of lime have the same molecular volume as is most 

 probable, then the sp. gr. of pure CaMo0 4 should be 200—46*9 

 = 4-267, if the molecular volume, 288 -f- 614 = 46 '9, is true 

 for scheelite. By means of the equation for the determination 

 of the sp. gr. of one constituent of a mixture containing two 

 substances of which one is known, the sp. gr. of CaMo0 4 is 

 4-3465 assuming the sp. gr. of CaW0 4 to be 6'14 and that of 

 the mixture 4*526 (sp. gr. of powellite). This close agree- 

 ment in these two calculations of the sp. gr. of CaMo0 4 is an 

 interesting and important confirmation of the chemical and 

 physical data which are given above. 



"When this investigation was nearly completed my attention 

 was called to a recent paper by H. Traube* in which was dis- 

 cussed the influence of certain varying quantities of molybdic 

 acid in scheelite upon the physical constants, namely, sp. gr. 

 and axial ratio. The following scheme is interesting in that it 

 illustrates those variations which different proportions of iso- 

 morphous mixtures of CaW0 4 and CaMo0 4 produce. .No 

 mathematical law seems to exist which will express these tran- 

 sitions. 



CaMo0 4 Powellite Scheelite CaW0 4 



$Mo0 3 72 58-58 



Sp.gr. 4*267 4-526 



u:c 1 : l*5458f l:l*5445j. 



I take pleasure in naming this new mineral species in honor 

 of Major J. W. Powell, Director of the United States Geo- 

 logical Survey. 



Chemical Laboratory of the U. S. Geological Survey, Washington, D. C, 

 December 11th, 1890. 



Art. XYIII. — Bruckner's Klimaschwankungen ; by 

 Frank Waldo. 



Dr. Edward Bruckner, the youthful professor of Physical 

 Geography at the University of Berne, has devoted three 

 years to the gathering together and discussion of data concern- 

 ing oscillations of climate as shown by direct observations 



* Neues Jahrbuch fur Mineralogie, Beilage-Band, vii, Heft 2, 1890. 

 \ 1. Th. Hiortdahl, Zeitschr. f. Kryst. xii, 413, 1887. 

 % Neues Jahrbuch, Beilage-Band, vii. 



S. W. Africa. 

 8*09 



Zinnwald. 



(1) (2) 



8*23 1*92 



O 



7*63 









5-96 



5*88 



6-06 



6*14 





1: 



l*5349f 



1:1-5315 



