28 



8. A Series of Ores and Rocks, Illustrating the gold ores now 



extensively mined in the so-called Potsdam sandstone of 

 the Black Hills, S. D. The specimens were collected 

 in July, 1S96, by J. F. Kemp, by whom they are exhibited. 

 The ores are mostly telluride of gold and its oxidation 

 products and are segregated along vertical fissures called 

 "verticals" in the vicinity of intruded phonolites and 

 other porphyritic rocks. The mineralized sandstones are 

 cellular in character. 



9. Leucite-phonolites, from the Leucite Hills, Wyo., col- 



lected and exhibited by J. F. Kemp, Columbia Univer- 

 sity. These curious and exceptional rocks were the first 

 leucite rocks discovered in America, and the second out- 

 side of the continent of Europe. They cap a series of 

 dissected mesas in the Bad Lands in southeastern Wyom- 

 ing. 



10. Suite of American Pottery Clays, feldspar and flint. 



12 specimens. Exhibited by Heinrlch Ries. 



Products of different grades made from these materials, 

 and series of photogi-aphs illustrating the clay deposits 

 and methods of manufacture. Described in 17th Ann. 

 Rept. U. S. Geol. Survey, pt. IV, 1897. 



1 1 . Suite of Fuller's Earth Specimens from the American 



localities. 15 specimens and photographs. Collected 

 and exhibited by Heim-ich Ries. 



This material is used for clarifying oils, and is rapidly 

 superceding animal charcoal for this purpose. Until 

 two years ago it was only found in commercial quantities 

 in England. 



12. Suite of Clays from Alabama. 10 specimens. Col- 



lected and exhibited by Heinrich Ries. 



Recent investigations show that Alabama has vast clay 

 resources, especially in her Cretaceous and Tertiary 

 formations. To be described in forthcoming bulletin of 

 the Ala. Geol. Survey by H. Ries. 



