AUGHET.] timbEk in modern geological times. 265 



zation advances westward. As early as the summer of 1865, 1 examined 

 the region at the headwaters of the Logan, Elkhorn, and Bow Rivers, 

 where I found many small ancient creek-bottoms, with stream-beds in 

 the center, or nearer one side, all grown over with a thick sod of grass 

 and weeds, and where the water had not flowed for ages. To be sure of 

 this couclasion, I dug down, at convenient places, to ascertain the condi- 

 tion of the subsoil. In almost every instance I found more or less shells 

 of fresh-water mollusks, so decayed that on the least exposure they 

 would crumble to pieces. They all belonged to the genus Vnio or Ana- 

 donta, the former seemingly being most abundant, but this probably 

 resulted from the greater fragility of the latter. I failed to identify any 

 species. Many of these localities I had marked. Already in 1871 many 

 of these old streams commenced again to flow, and since then many 

 more have become supplied with apparently permanent water. Many 

 springs of water, too, are bursting out along bluffs where nothing of the 

 kind was known before. It is probable' that the great amount of land 

 broken up and cultivated absorbs more of the falling rains than could 

 have been taken in by the hard prairie. Let any one carefully watch a 

 slope, one-half of which is plowed deeply, and the other half yet virgin 

 prairie, during a heavy rain ; the former will absorb all the water that 

 falls, while it runs off the latter in currents. The constant evaporation 

 of this increased water-supply must, in the nature of the case, produce 

 more vapor in the atmosphere. In my opinion, however, we may ac- 

 count for it. There is little room to doubt that the atmosphere is becom- 

 ing more moist or the rain-fall is increasing, or both, all over Eastern 

 and probably Western Nebraska. The great change constantly going 

 on in the flora of the State points to the same conclusion. The grasses 

 especially and the sedges characteristic of dry regions are rapidly re- 

 treating, and in many places disappearing altogether, while others, that 

 are more peculiar to moister regions, are taking their places. Hayden, 

 from a most careful study of a partially different class of facts, long 

 since came to a similar conclusion. (See his report for 1870, j). 455, &c.) 



TniBEE IN MODERN GEOLOGICAL TIMES. 



It is natural to suppose from well-known natural causes that when 

 the Loess age was drawing to a close, and the lower portions of the area 

 covered by these deposits was yet in the condition of a bog, the climate 

 was much more favorable than the present for the growth of timber. 

 Eainfall and moisture in the atmosphere must then have been much 

 more abundant. In July, 1868, while walking along the edge of one of 

 the Logan peatbogs in Cedar County, my jacob-staff struck some hard 

 body in the peat. Examining it more closely I found a log buried in 

 the peat at least sixty feet in length. Following up this discovery with 

 a careful search, I found in this and other bogs a great many buried logs 

 of various length and thickness. Most of them were found where there 

 was no existing timber within twenty miles, and from which they could 

 not have floated in flpod-times. I regTet that I had no means of extri- 

 cating some of those logs, and ascertaining the species to which they 

 belonged. That would no doubt have thrown much light on the changes 

 that have taken place since they were buried in the bog. But they evi- 

 dently grew on the shores or banks, and after failing into the bogs they 

 were protected against decay by the well-known antiseptic properties of 

 peaty waters. Another fact that shows the greater prevalence of tim- 

 ber within geologically recent times is the remnants of old pine-forests 

 yet buried in the ground. In the summer of 1868, when traveling along 



