Report of National Museum, 1893. 



Plate 21. 



SELENITE CRYSTALS.— From cave in 



what is locall\- known as the South Wash, in 

 Wayne County, Utah. 60,881. 



Received from J. E. T.\i,m.\ge, 1893. 



The crystals occur in a cave which is inclosed by a 

 thick shell forniinjj a mound which stands in relief on a 

 hillside as shown in the photograph. The crystals vary 

 greatly in size and weight, some being over four feet 

 long. Owing to the vandalism of visitors, it has been 

 found necessary to remove the finest specimens to the 

 Deseret. Museum, at Salt Lake City, to prevent their com- 

 plete destruction (See Science, Feb. 17, iSgj ) 



CORRODED STALACTITE.— The specimen is 

 partial!)- dissolved by the corroding action of water 

 from the roof. It illustrates one of the latest stages 

 in the life history of a cave. The liine in the over- 

 lying roof has been so far removed that the water 

 percolating though it is still acid and attacks the 

 material of the stalactites as it drips over them. 



Robertson's Cave, Springfield, Missouri. 68,186. 



Collected by George P. Merrill, 1892. 



-.^^^ 



VOLCANIC DUST. 



Volcano of Kr.\k.\toa, Str.iits of Suiida. 36,974. 



Gift of F. W. Houghton, 1889. 



This ash was showered for three days in September, nnd 

 at the rate of one inch per hour, on board ship Beacons- 

 field while in l.ititude o'^ 14' S., longitude 9;'^ E., and at a 

 distance of 855 miles from the source of eruption. 



ORTHORHOMBIC SYSTEM. 



DISTINCTIVE CRYSTALS ON MATRIX. 



A comtinalicn of llic Basal I'Line (001, O) .infl a Bracliyprism {izo.ii) 

 «ilh a Brachylome {041. 4;) aii.-| tivo rjranml.^ (J2J, ;'j.and ill, (), 

 slightly modified by the Unit Prism (110, /), 



TOPAZ 

 with Albite, Muscovite and Smoky Quartz. 

 ALAbA^CHKA, Ural Mountains. Sil-tna 



Leidv Collection 



Specimen forms of labels. 



