AUGHET.] 



LIFE OF THE LOESS AGE. 



255 



ajnericanus). Unfortunately this vertebra partially fell to pieces on ex- 

 posure. It appears clear from this conjunction of a human relic and 

 proboscidian remains that man here as well as in Europe was the cotem- 

 porary of the elephant in at least a portion of the Missouri Valley. 



A 



mi 



B 



mz 



Arrows found in tlie Loess. 



No. 1. Found three miles east of Sioux City, Iowa, fifteen feet below 

 the surface. 



Xo. 2. Found two miles and a half southeast of Omaha, Nebr., twenty 

 feet below the surface and beneath a vertebra of an elephant. 



The nlimate probably varied considerably during the progress of this 

 age. What inclines me to that view is the fact that about the middle 

 horizon an unusually large number of southern species of mollusks are 

 found. This indeed is not conclusive, as this region is at this time re- 

 markable for the presence of southern forms of insects and fresh-water 

 mollusks.* Yet it appears to me that the unusual number of southern 

 forms at this horizon of the Loess must indicate some modification of 

 climate at that period. It may have been only on the eastern shore of 

 this great lake, and caused by the even temperature which so large a 

 body of fresh water produces on the side toward which the prevailing 

 winds from the lake blow. We have such a phenomenon at the present 

 day on the east shore of Lake Michigan. The Mississippi Valley is by its 

 contour eminently favorable to the emigration northward of southern 

 species. 



These Loess deposits, which have done so much to enrich Nebraska, 

 have received profound attention and study from some of the ablest 

 geologists. But in more than one-half of the counties of the State they 

 have not yet been investigated. Much to be discovered must yet remain 

 in them. Though myself long engaged in their investigation, I rarely 

 examine a new section in a well, ravine, or railroad-cut without finding 

 something new. 



* Hayden's Report for 1870, p. 467. 



