28 THE NORTH AMERICAN INDIAN SUMMER. 



regions of the sun. Mild and balmy though the climate 

 upon the plains may generally be towards its equatorial 

 margin, its alternations are elsewhere almost always 

 very great; the summers, even far up towards the 

 polar circles, being generally very hot ; and the winters 

 correspondingly cold ; but at all seasons sudden variations 

 of temperature are always liable to occur. Thus, the 

 heats of summer will be suddenly found to change to 

 cold; on the other hand, even during the severest 

 winters, mild days will occasionally intervene; the springs 

 and autumns too are apt to alternate with periods of 

 hot and cold weather, which are sometimes very trying. 

 A good, and generally well marked illustration of this 

 may be found in what is called in America " The 

 Indian Summer." This occurs during the "fall," or 

 autumn, and is often preceded by periods of consider- 

 able cold : when suddenly the scene changes, and summer 

 appears to come back again ; a balmy softness fills the 

 air, while the horizon is generally somewhat obscured 

 by a species of smoky haze. This condition of things 

 may continue for periods varying from a few days to 

 a fortnight, or more; after which the breaking up of 

 the Indian Summer is generally the precursor of wintry 

 weather. 



Notwithstanding its changeable character, and the 

 sudden alternations of hot and cold periods, the climate 

 throughout the region of the great plains may be 

 described on the whole as peculiarly healthy; and 

 malarial diseases of malignant type may be said hardly 

 to exist here. We do not mean to say that incautious 

 exposure during hot weather, to the miasma of swampy 

 districts, may be practised with impunity; but even 

 there, fevers of malarial origin, when they do occur, 



