26 PHYSICAL GEOGRAPHY. 



one hundred miles west of the Missouri. This line enters the 

 State near its northwest corner, and then passing southeast, and 

 then in an easterly direction, slightly north of a line half way be- 

 tween the Platte and the north line of the State until it reaches 

 within about one hundred miles of the Missouri. It then makes 

 an angle, turning to the northwest, and mainly keeping that direc- 

 tion until it strikes the mouth of the White Earth River. Cross- 

 ing Northern Iowa, it strikes the northwest corner of Illinois, then 

 turns northeast to Green Bay, and thence to the coast by way of 

 the Straits of Mackinaw. From this it appears that all of Ne- 

 braska, except the small part north and west of the line just de- 

 scribed, has an average temperature like Northern Illinois and 

 Ohio. The portion north and west of the line described has a 

 mean winter temperature slightly lower, if the Smithsonian data 

 can be trusted. The number of observations, however, on which 

 this isochimal line was based through Northern Nebraska were no- 

 toriously few and imperfect. My own conviction is that future, 

 more perfect data will assign the whole of Northern Nebraska to 

 at least the isochimal line of 20. 



MEAN TEMPERATURE AND CHARACTER OF SPRING. 



The next season of greatest interest is that of spring. What in 

 other words is the mean temperature of March, April and May ? 

 The best exhibit of the spring temperature is found in Dr. Childs' 

 table, " B." From that it is seen that the mean temperature of 

 spring for the last ten years was 47, 47'. The reports of the 

 Signal Offices at Omaha and North Platte do not differ materially 

 from this determination. The Nebraska Weather Service, inaug- 

 urated first by Prof. Bailey, and now conducted by Prof. Thomp- 

 son, Superintendent of Public Instruction, gives the following 

 bulletins for the spring months confirmatory of the above, with 

 additional facts of great importance : 



Bulletin for March. " Highest temperature recorded, 92 at 

 Palmyra, at 2 p. M., on the 2yth; lowest 21, at Desota, on the 

 1 4th. Average noon observations for the whole State, 52. Low 

 est noon temperature 15, on the ist. Highest noon temperature 

 92, on the 27th. Average of all the observations gives the tern 

 perature of the ist at 20, and of the 2yth at 86. Four stations 

 report over an inch of rainfall, viz.: Weeping Water, 1.25 of an 



