FOREST GEOGRAPHY AND ARCHAEOLOGY. 215 



the different views taken upon this knotty question. The only 

 settled thing about it is, that the prairies are not directly due 

 to a deficiency of rain. That the rain-charts settle, as Pro- 

 fessor Whitney well insists. 



The prairies which indent or are inclosed in our Atlantic 

 forest region, and the plains beyond this region, are different 

 things. But as the one borders — and in Iowa and Nebraska 

 passes into — the other, it may be supposed that common 

 causes have influenced both together, perhaps more than Pro- 

 fessor Whitney allows. 



He thinks that the extreme fineness and depth of the usual 

 prairie soil will account for the absence of trees ; and Mr. 

 Lesquereux equally explains it by the nature of tlie soil, in a 

 different way. These and other excellent observers scout the 

 idea that immemorial burnings, in autumn and spring, have 

 had any effect. Professor Shaler, from his observations in the 

 border land of Kentucky, thinks that they have, — that there 

 are indications there of comparatively recent conversion of 

 Oak-openings into prairie, and now — since the burnings are 

 over — of the reconversion of prairie into woodland. 



I am disposed, on general considerations, to think that the 

 line of demarcation between our woods and our plains is not 

 where it was drawn by Nature. Here, when no physical bar- 

 rier is interposed between the ground that receives rain enough 

 for forest and that which receives too little, there must be a 

 debatable border, where comparatively slight causes will turn 

 the scale either way. Difference in soil and difference in expo- 

 sure will here tell decisively. And along this border, annual 

 burnings — for the purpose of increasing and improving Buf- 

 falo-feed — practised for hundreds of years by our nomade 

 predecessors, may have had a very marked effect. I suspect that 

 the irregular border line may have in this way been rendered 

 more irregular, and have been carried farther eastward wher- 

 ever nature of soil or circumstances of exposure predisposed 

 to it. 



It does not follow that trees would reoccupy the land when 

 the operation that destroyed them, or kept them down, ceased. 

 The established turf or other occupation of the soil, and the 



