GEOLOGY IN NATIONAL MUSEUM MERRILL. 279 



Attention may also be called to the peculiar curved and distorted 

 stalactitic forms from this same cavern and the fluted and otherwise 

 corroded blocks of limestone illustrating the solvent action of car- 

 bonated waters in the formation of caves. The bottle and wineglass 

 coated with the calcareous deposit illustrate the comparative rapidity 

 with which the deposition may take place under favorable conditions, 

 while the mummified rat testifies to the dryness of the older portions 

 of caves like Mammoth and Marengo, where solution and refilling 

 processes have practically ceased. 



Following this somewhat extended series are two cases likewise 

 filled with products of water solution and deposition, but of a some- 

 what different nature. The more striking are the mushroom-shaped 

 tufas formed through the gradual evaporation of the calcareous 

 waters of Pyramid Lake in Nevada, and the trunklike chalcedonic 

 forms lined with crystalline quartz or calcite from southeastern 

 Wyoming. 



VOLCANOES AND VOLCANIC PHENOMENA. 



The collections are designed to show by means of maps, models, 

 illustrations, and actual specimens as much regarding volcanoes in 

 their active and incipient stages as space will permit. 



The general scope of the exhibit is as below : 



(1) Volcanic products, shown by specimens selected to 

 illustrate (a) characteristic forms of lava, as slaggy, pumi- 

 ceous, glassy, compact, columnar; volcanic bombs, lapilli, 

 sand, dust, etc.; (h) kinds of lava, both ancient and 

 modern ; (<?) kinds ejected by the same volcano at different 

 periods of eruption ; (d) chemical products. 



(2) Specimens showing contact phenomena and secondary 

 minerals. 



(3) The economy of volcanoes and allied phenomena, 

 shown by chemical products, as sulphur and other sublima- 

 tion products, pozzuolana. building stone (lavas and tuffs), 

 travertines. 



The most striking of the objects in this exhibit are the pumiceous 

 (bread crust) bombs from Lipari ; the stalactitic lavas and Pele's hair 

 from the Hawaiian volcanoes; the large masses of obsidian and 

 pumice from the Yellowstone Park and Mono Crater, and the basaltic 

 columns from Rhenish Prussia (pi. 12, fig. 2). 



THE YELLOWSTONE NATIONAL PARK EXHIBIT. 



The Yellowstone National Park, situated in the extreme northwest- 

 ern portion of Wyoming, comprises an area of 2,142,720 acres. The 

 central portion is essentially a broad, elevated plateau between 7,000 



