18 Transactions of the 



The Pliocene gave us bones of deer, beaver, a larger animal of the ox family, two spe- 

 cies of horse, less in size than our smallest Indian ponies, a wolf, ivory from the mastodon 

 or elephant, bones of the rhinoceros and camel, also some remains of an undetermined 

 character. In addition to these we have the bones and carapace of a large fresh-water 

 turtle, five feet in length, and a few obscure marine fossils ; also what appear to be the 

 casts of stems of water-plants. All these, as may readily be considered, are of extinct 

 species, and some of extinct genera. All the bones are fossilized, and most of them 

 change to hard, compact silica. The most interesting of these is the ivory. In the pro- 

 cess of petrifaction, the tusk must have been so softened as to admit the intermixture of 

 black oxyd of manganese* in solution, wliich then crystalized in delicate sprigs. The 

 ivory was then silicified into nearly pure quartz, with the hardness of that substance. 

 Thus we have the ivory convei-ted to the so-called moss agate. Some fragments could 

 not be detected in appearance from that gem. Specimens of it have been sent to the cab- 

 inet of Yale, and a few are deposited in our collection of the Kansas Academy of Science.f 

 The agencies of nature that changed this ivory to a silicious moss agate must have been 

 somewhat similar to the hot springs of Iceland and the Yellowstone Park. Those springs 

 will change organic substances to silica — the only known natural agency which will do 

 so in a thorough manner. 



Tlie materials of the Tertiary-Pliocene are in as strong contrast with those of the Cre- 

 taceous as are the fossils. While the latter is composed of fine-grained chalk and shales, 

 the former is of silicious sand, in many places intermingled with coarse pebbles of meta- 

 morphic rock. For the most part, the sandstone is in a very friable state, crumbling on 

 exposure to the atmosphere; and where it is more compact, its mechanical composition is 

 80 irregular as to render it almost entirely unfit for a building material. When firmly con- 

 solidated, it forms the tops of the table-like hills of northwestern Kansas. At Bread-Bowl 

 Mound, in Phillips county, it is nearly two hundred feet above the water of Deer creek, 

 and at Sugar Mound, in the western part of Rooks county, which is nearly three hundred 

 feet above the waters of the Solomon, it forms seventy-five feet of the upper portion. Far- 

 ther west, it occupies the whole of the visible deposit, and the mounds are not so promi- 

 nent. On Prairie Dog creek, in Norton county, it is about four hundred feet in thickness. 

 Beyond, westward, we have reason to believe that the formation is still thicker. Our time 

 and engagements have never allowed us to visit in the extreme western counties. 



The occurrence of moss agates (as they are called) on the plains, in the western part of 

 the State, is well known. Beautiful specimens have been picked up, and are frequently 

 worn as jewelry. As they are found in the loose gravel, they liave been supposed to owe 

 their present deposit to drift, their original home having been in the North. But I was 

 somewhat surprised to find that they originated in tlie Pliocene deposit, within the 

 bounds of western Kansas, near their present position. In Wallace county, tliis Pliocene 

 consists of a silicious deposit, formed of material varying from coarse flint-quartz, to 

 chalcedony, milk-white to transparent ; sometimes presenting a fine semi-opal appearance 

 Oxyd of manganese, more or less crystalized in minute, moss-like sprigs, extend through 

 the whole strata of eight feet. Tlie lower part is formed of the coarser materials, and it 

 is only in the upper six inches that we find any moss agate fit for the lapidary. Some of 

 them are very fine and transparent. The whole mass is extremely interesting to the min- 

 eralogist, as showing tlie moss agate in the whole process of formation. The lower 

 portion indicates an imperfect chemical solution of the silica and oxyd of manganese, 

 therefore the crystalization is imperfect ; while the upper inch, or half-inch, contains the 

 best specimens, evincing the deposit in a higher state of chemical development. 



The fossil ivory must have been subjected to this same chemical process. Tliis deposit 

 I first noticed as the broken cap-rock of the two buttes two miles southwest of Sheridan, 



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* On a chemical test, by Prof. Kedzie, some iron was found with the manganese. 



t They wore submitted to the inspection of the members at the reading of this article. • 



