266 GEOLOGICAL SURVEY OF TIIE TERRITORIES. 



and near the Niobrara, roots of pine trees were often found sticking in 

 the ground, more than fifty miles south and east of the present forests 

 of this timber. Often did these old roots furnish me with the materials 

 of a camp fire. At no very remote period pine forests must have flour- 

 ished down to the mouth of the Niobrara. Many other facts, of a simi- 

 lar character, seem to leave no room to doubt that in geologically recent 

 times far more extensive forests prevailed all over Nebraska than those 

 which now occupy the ground. What caused their disappearance can, 

 perhaps, not be certainly determined. Some geologists hold that the 

 increasing dryness of the climate caused the disappearance of any old 

 forests that might have existed. But might not the converse of this 

 also have been true here, as well as elsewhere, namely, that the destruc- 

 tion of forests inaugurated th^ dry climate that prevailed when this ter- 

 ritory was first explored "\ It is at least conceivable that the primitive 

 forest received its death-blow in a dry summer by fire, through the van- 

 dal acts of Indians in pursuit of game or for purposes of w r ar. What 

 suggested this theory as a possible explanation of the disappearance of 

 forests on this territory, was the finding of the pine-roots before referred 

 to, and often, when partially buried, showing marks of fire from carbon- 

 ized ends, and in localities so sandy, and where vegetation was so scant, 

 that an ordinary prairie-fire was out of the question. An old tradition, 

 that J once heard from the Omaha Indians, points to the same conclu- 

 sion. 



It is wonderful how nature here responds to the effort of man for re- 

 clothing this territory with timber. Man thus becomes an efficient agent 

 for the production of geological changes. As prairie-fires are repressed 

 and trees are planted by the million, the climate must be still further 

 ameliorated. When once there are groves of timber on every section 

 or quarter-section of land in the State, an approach will be made to 

 some of the best physical conditions of Tertiary times. The people of 

 this new State have a wonderful inheritance of wealth, beauty, and 

 power in their fine climate and their rich lands, and as they become con- 

 scious of this they will more and more lend a helping hand to the pro- 

 cesses of nature for the development and utilization of the material 

 wealth of Nebraska. 



MOLLUSKS IN THE LACUSTRINE DEPOSITS. 



The following list of land and fresh-water shells comprise all that I 

 have thus far identified, in whole or in part, from the Lacustrine deposits. 

 Nearly all are extremely fragile. The Hyalinas, Pupas, and some of the 

 Helices long eluded my efforts at identifying them. I finally marked 

 the localities where found until the ground was frozen, when they were 

 cut out with a knife. They were then identified by making thin sec- 

 tions with a sharp knife. Many of these mollusks, after being placed 

 for a while in my cabinet, fell to pieces. For this reason, I have no 

 specimens to show of many species here given, and, therefore, only pre- 

 sent this as a provisional list. Some well-preserved specimens appear 

 to me to be new to science, but as I have not access to the descriptions 

 of the new species discovered by Hayden, a bare list of which is given 

 in Binney and Bland's Land and Fresh Water Shells, I will not ven- 

 ture to describe them, as that has probably already been done. The 

 counties are indicated where the specimens were obtained, or where 

 they were the most abundant: 



Vitrina limpida Gould, Lancaster and Dixon Counties. 



Jlyalina nitida f Miiller, Dixon County, 



