STATE HORTICULTURAL SOCIETY. 403 



raise a block of granite as large as a township and 100 feet thick 

 to a height of over 800 miles above the level of the sea. 



Yet with all this stored up heat, representing a power compared 

 with which that at the same time buried in the earth is as a 

 €orliss engine beside a mere toy, our climate is subject to sud- 

 den changes. With nothing to break their course the northerly and 

 northwesterly winds are cold — those of winter sweeping down over 

 the prairies of Dakota, extremely so. The difference between the 

 warmest summer day and coldest winter night is about 120®. 

 Our average temperature for the 18 years ending with 1883 was, 

 according to Mr. Wm. Cheney, 42.52'^. With this general average 

 we have an average January temperature of near 12'^ and a July 

 average near 71°, which latter figure certifies to a climate capable 

 of ripening the finest grapes. But the averages are not what the 

 farmers fear; the sudden changes and the minima are destructive. 

 All parts of the country away from the seaboard are subject to these 

 abrupt variations, yet the climate is affected but slightly by them. 

 The two factors having a constant climatic effect are — distance 

 from the equator and elevation above the sea. According to Prof, 

 Samuel Haughton* the variation for our latitude and longitude is 

 2.20* Fahr. for each degree of latitude, a co-efficient which is true 

 for only a small part of the earth's crust. For if we pass north or 

 south, east or west 10*^ a different coefiicient is found. So, too, in 

 the variation of the temperature with the altitude the co-efiicient is 

 found to vary with different continental areas and even with differ- 

 ent parts of the same continental area. For the central position 

 which Minnesota occupies, the reduction in temperature must be 

 taken at about one degree for every 350 feet altitude. For exam- 

 ple Chatfield, at a height of 1285 feet, will average, other things being 

 equal, nearly two degrees colder than Winona. But the exposed 

 situation of the former and the protected situation of the latter, 

 no doubt make a greater difference than mere altitude would sug- 

 gest. 



Both rainfall and temperature are modified by other circum- 

 stances than altitude above the sea, geographical position and direc- 

 tion of mountain chains. The condition of the soil and the distri- 

 bution of forest and prairie, must be taken into the account. Prof. 

 Aughey, in his work entitled Sketches of the Physical Geography 

 and Geology of Nebraska, points out the gradual increase in the 

 rainfall of that state due to breaking the prairies and making the 

 soil lighter and more porous under the plow. By this means much^ 

 *Six Lectures on Physical Geography, Dublin, 1880, p. 108. 



