IOWA ACADEMY OF SCIENCES. 97 



principles. Our country is not too cold, neither is it too dry; 

 the rainfall in eastern Iowa being almost, if not quite as great 

 as in Indiana, where the primeval forest was once heaviest. 

 Indeed the uniformity of general conditions raises the prob- 

 lem: there seems to be nothing to hinder, therefore why is not 

 the forest universal? 



Various answers have been given to this question,^ 

 The opinion first entertained and that which is generally still 

 current among common people, was that the continental forests 

 were limited by fires. The Indians started fires and these fires 

 were slowly, at the advent of the white man, consuming the 

 woods, had stripped large areas in the Mississippi valley and 

 unchecked would eventually have reached the Atlantic coast. 

 No one who has been an eye-witness of the conflagrations that 

 once rolled in annual tides across Iowa or Illinois can doubt the 

 force of the theory so long and so widely entertained. The 

 difliculty lies in the fact that the forest stood the attack so well, 

 in fact seemed largely unaffected, actually held its own in 

 nearly every part of the fire-infested district. Then again, if 

 the truth had been that the aborigines were destroying the 

 woods at the time when the whites first became witnesses, proof 

 of the fact should be found over the whole region in form of char 

 red lags, stumps, etc., of which, needless to remark, there has 

 been no trace whatever. The fire theory not wholly satisfac- 

 tory, some students went to the other extreme and urged that 

 the distribution of the woods was due to causes efficient in 

 times remotely past, so that fires or present conditions had 

 nothing at all to do with the matter; the solution of the prob 

 lem must be sought in some earlier geologic age. 0:hers 

 again sought to solve the problem by a priori method. It Wiis 

 urged that trees exhaust the soil of one set of elements while 

 grasses, herbaceous plants, demand something entirely differ- 

 ent, so that either set of plants occupying for long ages a given 

 region would exhaust its availability though leaving the ground 

 serviceable for something else. Thus trees once occupied the 

 whole Mississippi valley but had exhausted the ground of tree- 

 material, so to speak, had worn out their welcome. The 

 answer to this is that here in Iowa trees seem to grow every- 

 where if planted and cared for. 



iSee inter al. Am. Journal of Science VI, 384: XXXVIII, 332 and 344; XXXIX, 317: 

 XL, 23 and 293. Geol. Survey of Illinois I, 238 ct xeq; Geology of Iowa, Hall, I. Part I, 

 p. 23 ct ifcq; U. S. Geol. Survey, Eleventh Annual Report of the Director, p. 3J6 ct seq. 



