622 EXHIBIT AT THE COTTON STATES EXPOSITION. 



suckle. These are the ancestors of many modern land animals now 

 inhabiting land areas other than North America. Among them were 

 very small horses with three toes on each foot, camels, tapirs, elephants, 

 etc. One of the characteristic sea animals of this time abounding in 

 the Gulf border region is the Zeuglodon Whale, a form related to both 

 whales and seals. A restoration of the skeleton of this long and slender 

 animal is shown suspended from the roof. The shelled animals of this 

 era at once remind us of living species. 



This collection also aims to show methods of displaying fossils now 

 in use in the Department of Paleontology. The fossils are cleaned of 

 all adhering rock, and when possible a series of each species is selected 

 to show specific varieties, being then glued upon encaustic tiles. The 

 advantage of tiles lies in the fact that they will neither fade nor warp, 

 are more uniform in size, and nearly as cheap as paper, or thin wooden 

 tablets. In cases where the attached specimens must be removed, this 

 can readily be accomplished by soaking in water without injury to the 

 tiles. 



DEPARTMENT OP GEOLOGY. 



In a single case in Alcove H was a collection illustrating the occur- 

 rence and association of gold and silver in nature, which is thus described 

 by Prof. George P. Merrill: 



The exhibit begins with a series of specimens showing both the native 

 metals and their compounds in the condition of greatest natural purity. 

 This is followed by a series of the same compounds with their charac- 

 teristic associations, but in which the metal-bearing portions are still 

 plainly evident, and this in turn by a third series showing selected 

 types of the ores as mined, but in which, as a rule, the metal or its 

 compounds are scarcely discernible. 



Attention is called to the fact that while gold, aside from its native 

 form, enters as an essential constituent into less tban half a dozen 

 known minerals, silver occurs in upward of six times as many. Thus 

 gold, aside from its natural alloys with silver (electrum), bismuth, and 

 palladium, is found in chemical combination with other elements only 

 in the minerals petzite, sylvanite, krennerite, and nagyagite. Silver, 

 on the other hand, is found native, as an alloy with gold (electrum), or 

 mercury (amalgam), and also as an essential element in compounds 

 forming nearly forty mineral species more or less well defined. 



Several of these compounds are very rare, and not at present included 

 in the series exhibited. 



It is further to be noted, that while both gold and silver occur either 

 as native or in compounds of such size as to be easily seen by the naked 

 eye, the great majority of ores of either metal are composed in large 

 part of other substances with which the metal is so finely and inti- 

 mately admixed as to be invisible and determinable only by chemical 

 means or where it occurs as a replacing constituent with other elements. 

 Thus the most common form of gold ore is an auriferous pyrite, while 

 the most common silver ore is an argentiferous galena. 



In the series as exhibited attention needs to be called, first to the 

 native gold, that is, the gold found in the metallic state in nature as 

 displayed in the form of nuggets, leaf gold, wire gold, and gold dust 



