172 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



The soils of this drift are usually gravelly, often stony, of variable 

 fertility, from the noted fertile lands of Ohio and Western Kew York to 

 the barren portions of New England. As a whole, these soils grow 

 liner as they go farther southward and westward from I^ew England 

 and Western Kew York. When overcropped and worn out, as often 

 happens, they recover when allowed to rest fallow several years by the 

 decomposition of the mingled materials of which they are composed. 



Alluvial soils. — These are formed from the deposits of fine, earthy 

 materials, sediment, silt, or detritus, by rniming streams and rivers, of 

 which we have such a notable example at the Mississippi's delta. " The 

 amount of transportation going on over a continent is beyond calcula- 

 tion, streams are everywhere at work, rivers, with their large tributaries 

 and their thousand little ones, spreading among all the hills and to the 

 summits of every mountain. And thus the whole surface of a couti- 

 nent is on the move towards the oceans. The word detritus means worn 

 out, and is well applied to river depositions. The amount of silt car- 

 ried to the Mexican Gulf by the Mississippi, according to the Delta 

 Survey under Humphreys and Abbot, is about yjVo of the weight of 

 the water, or ggL^ of its bulk, equivalent for an average year to 

 812,500,000,000,000 jjounds, or to a mass 1 square mile in area and 241 

 feet deep. (Dana's Geology, p. 648.) 



These constitute the "bottom lands," as they are called in the West. 

 The Red River region, which has become famous as a wheat-producing 

 country, lying partly in Minnesota and partly in Dakota, occupies the 

 bed of an ancient lake, known to geologists as Lake Agassiz, and is com- 

 posed of a black sedimentary soil, exceedingly fine in texture, and very 

 fertile and deep. This tract extends southward to Lake Travers, on 

 the Red River, widening as it proceeds northward and extending on 

 both sides of the river 50 or 60 miles wide where its bed leaves this 

 country, and expanding to much greater width in Manitoba. 



The further westward soils of this class are found the less the amount 

 of organic matter they contain, until in the valleys of California are found 

 soils of great fertility which contain an exceedingly small amount. Of 

 course such soils, as those of California just mentioned, are deficient in 

 the faculty of storing up water for future use, and, however rich they 

 may be in mineral constituents, yet in a dry region or one subject to 

 periodical droughts, irrigation would have to be resorted to in order to 

 get large yields of crops. 



Soils of disintegration. — These occupy the undulating parts of this 

 country lying south of the drift, possessing every variety of character, 

 both in regard to their chemical composition and physical properties, as 

 their mode of formation indicates, arising from the disintegration of the 

 subjacent rocks by atmospheric agencies. 



Where the underlying rock has been an impure limestone, containing 

 much insoluble matter, the carbonate of lime has been slowly dissolved 

 out by the action of the carbonic acid contained in the rain, leaving the 

 insoluble matter behind. Such soils as that of the " bl^ie-grass " regions 

 of Kentucky are so formed, and are often of extreme fertility. (See the 

 Kentucky Geological Reports for further details about this region, in- 

 cluding the chemical analyses of its soils.) 



Professor Whitney states that some of the prairie soils of Iowa, par- 

 ticularly those where the soil is of nearly impalpable fineness, have 

 been produced by the slow action of atmospheric agencies on beds of 

 limestones which formerly occupied their places. In the course of time 

 the soluble carbonate of lime was gradually dissolved out and carried 

 away by the rivers and streams to the ocean, and a small amount of in- 



