1881.] NATURAL SCIENCES OF PHILADELPHIA. 13 



still increase their area annually, but trees could never get far 

 beyond the line they had reached when the annual fire first com- 

 menced. There could be no doubt that an annual burning in a 

 tract destitute of forest growth, would certainly prevent the 

 spread of timber, or of any plant that required more than a year to 

 mature seed from the time of sowing. Now, if we look at the 

 actual facts, we find that the Indians did annually fire the prairies. 



Father Hennepin, the earliest writer on Indian habits, noted 

 that it was the practice in his time. There is little doubt but this 

 practice of annual burning has been one extending long into the 

 past. What object had they in these annual burnings ? They 

 must have known that the buflTalo and other animals on which 

 they were largely dependent for a living, throve only on huge 

 grassy plains, and that it was to their interest to preserve these 

 plains by every means in their power. Low as their power of 

 reasoning may be, they could not but have perceived that while 

 grassy herbage throve in spite of fires, perhaps improved under 

 the fiery ordeal, trees could not follow on burned laud. What 

 could be more natural than that they would burn the prairies with 

 the object of retaining food for their wild animals ? If we have no 

 difficulty in reaching a positive conclusion so far, we may now 

 take a glance at the early geological times. Mr. Meehan then re- 

 ferred to the researches of Worthen, Whittlesley and others in 

 Ohio, Illinois and other prairie regions. On the retreat of the 

 great glacier, the higher lands and drift formation were probably 

 high and dry long before the immense lakes formed from the 

 melting and turbid waters ceased to be. 



It was tolerably well understood that many species of trees 

 and other plants which required a temperate atmosphere, retreated 

 southward!}^ with the advance of the glacier, and advanced to 

 higher latitudes on the glacier's retreat. Thus these higher ridges 

 would become timbered long before the lower lands became dry. 

 Evidence accumulates that man existed on this continent, in the 

 far west, not long after the glacier retreated, though '"not long," 

 in a geological sense, may mean many hundreds of years. The 

 lakes of glacial water would gradually become shallower from 

 the deposit of the highly comminuted material brought down 

 from higher land, from the wearing away of rocky breastwoi'ks as 

 in South Pass, Illinois, as well as from the openings which would 

 continually occur from nature's ever varying plan of streams 

 under ground. In all events, the drying of these lakes would be 

 from their outward edges first. Aquatics would give way to 

 marsh grasses, and these to vegetation such as we now find gener- 

 ally spread over the prairie region. If now we can conceive 

 of human beings such as we know the Indian races to be, al- 

 ready in more southern latttudes — having learned the fact that 

 firing would keep down trees and aid in the preservation of the 

 chase — following the retreat of the glacier to the higher lands, and 

 still as they advanced northwardly, firing the plains up to the 



