576 



METASPERMAE OF 'i HE MINNESOTA VALLEY. 



till soil is the most prominent in the Minnesota valley and oc- 

 curs in both prairie and forest region. It is somewhat more 

 fertile than the red till and second as a subsoil only to the al- 

 luvium. The fertility of any soil is, however, secondary so far 

 as concerns the subscil and it is to the layer of loam which 

 covers the till that the productive qualities must largely be re- 

 ferred. The loam varies in its per cents, of nitrogenous sub- 

 stance, but in general maintains a high average. 



Climate. Owing to the short time during which meteorolog- 

 ical observations have been made in the valley of the Minneso- 

 ta it is not pos'jibie to get all the data that are desirable for an 

 explanation Ox its climate. Prom the statistics compiled for 

 the Smithsonian Institution, by Schott, I am able to present 

 the following table of mean annual and seasonal precipitation 

 at certain pc'ats of interest. 



TABLE OF PRECIPITATION. 



In this table the figures are means arranged from observa- 

 tions extending over various periods. The precipitation is 

 sriven in inches and fractions. 



At Ft. Snelling the maximum annual precipitation during 

 the period was in 1849 when 49.69 inches of water was precipi- 

 tated. The minimum was in 1852 when 15.07 inches was pre 

 cipitated. The observations extend from 1837 to 1874. 



At St. Paul the maximum was in 1865 when 38. 14 inches felL 

 The minimum was in 1864 when 14.86 inches fell. 



The mean yearly precipitation, as indicated upon the iso- 

 hyetal maps prepared by Schott, varies in the Minnesota valley 

 from 20 to 82 inches. It is greatest in the region around Ft. 

 Snelling and least in the high land of the western boundary. 



Por the spring, summer and autumn the mean precipitation in 

 the delta region of the Mississippi is respectively 18 inches, 

 and for the same region the winter precipitation is 16 inches, 

 Making a total mean precipitation of 70 inches. 



