14 



The Vegetation of the 



great, not to be considered as more constant, as well as those between the 

 latter part of May and the end of July. 



Comparing the result of the thirty years observations with the march 

 of temperature of a single year we find the latter much more irregular. 

 In 1858 after a very mild January followed a severe February, and the 

 first decade of March was colder than the first decade of January. In 

 1869 the first decade of February was the coldest of that winter and March 

 colder than January. 



The mean temperature of Peoria is about the same as that of Paris, 

 in France, under 48° 50' north latitude, that is 8° farther north than 

 Peoria. We find for spring and fall about the same temperature in both 

 localities, but a great difference for summer and winter. 



Rome, in Italy, about 1° farther north than Peoria has a mean tem- 

 perature of 60.8, in summer 74.3, in winter 50. That makes the mean 

 temperature of Rome about 9° and in winter 22.6° warmer than in 

 Peoria and the summer is nearly 1° colder. These examples may be suffi- 

 cient to show the difference of climate of western Europe and the central 

 parts of North America. 



