1900. 



AMERICAN FORESTRY ASSOCIATION. 



241 



ever I have traveled in the State since the 

 presentation of my last paper, I have 

 found additional proof of its truth. I 

 have the utmost confidence that the tim- 

 ber areas are much larger where they have 

 been protected than they were twenty or 

 thirty years ago. 



In this connection I may quote from a 

 private letter written to me by Professor 

 Blankinship, of the Montana State College 

 of Agriculture and Mechanic Arts. In a 

 conversation with him on this subject in 

 June he spoke of having observed the 

 same thing in southern Missouri. 



"The line between forest and prairie 

 runs from the southwestern corner of the 

 State, northeastwaixl to the Mississippi 

 somewhat north of St. Louis. Greene 

 County is on that line and it was there 

 that I studied the subject, and the fact 

 of forest extension is very evident. This 

 county is about half prairie and these 

 prairies are now confined to the higher 

 uplands of that region, the timber appar- 

 ently having followed up the water-courses 

 and united in the broken ground at their 

 heads, leaving the prairies as mere islands 

 in the on-coming forest; westward the 

 prairies are larger and we pass in about 

 thirty miles from the unbroken forest to 



j 



the plains with streams scantily forest 

 clad. From the united evidence of the 

 old settlers, I found that the timber had 

 encroached on these prairie islands about 

 one mile in the last fifty years, and that, 

 too, despite the fact that it was being con- 

 stantly cut for log houses and particularly 

 for fencing purposes and fire-wood." 



IS INCREASED RAINFALL THE CAUSE? 



If we take up the question of the cause 

 or causes concerned with this very evident 

 increase in the timber areas we are face 

 to face with a very difficult problem. It 

 has been held by some observers that the 

 principal cause is the increased rainfall 

 upon the prairies and plains. In Nebraska, 

 however, we have learned that the sup- 

 posed increased rainfall is an error. It is 

 true that fifteen or twenty years ago we 

 had publications which seemed to be quite 

 authoritative, in which the supposed in- 

 creased rainfall was discussed ; and there 



were maps drawn, even, to show how 

 year after year the rain belt moved west- 

 ward. As you are aware, Professor 

 Swezey, of the University of Nebraska, 

 has entirely overthrown this theory. His 

 careful studies of the rainfall through long 

 periods of time show that while there are 

 short periods during which there is an 

 increase in the rainfall, there are other 

 periods in which there is a corresponding 

 decrease. It is his opinion that there is no 

 ground at the present time for the belief that 

 the rainfall in Nebraska has increased dur- 

 ing the period of its settlement. There can 

 be no question that we must throw out of 

 the discussion the theory that an increased 

 rainfall has brought about this increase in 

 the forest areas. 



IS CHANGE OF TEMPERATURE A CAUSE? 



It is sometimes said that other climatic 

 changes than those directly connected with 

 the rainfall have had to do with this in- 

 crease in the timber areas. We hear the 

 statement made that the climate is slowly 

 changing, even where the increase in rain- 

 fall is not insisted upon. Now the cli- 

 mate of a country includes a number of 

 factors. Moisture is one of the most im- 

 portant of these. Next to this perhaps 

 may be placed temperature, and then wind, 

 light, etc. With respect to these factors 

 we have no indication whatever from a 

 careful study of the meteorological data 

 that there has been any permanent change 

 in the temperature of the prairie and 

 plains region. Our climate is neither 

 growing hotter nor colder. Here again 

 we find that we may have a series of years 



/ * 



in which the temperature is increased, and 

 then a series in which it is decreased, but 

 no permanent change has been observed 

 either in the way of an increase or de- 

 crease in the temperature. 



IS LESSENED WIND A CAUSK ? 



With respect to the winds, this only can 

 be said, that as the ground is more and 

 more covered with tall-growing vegeta- 

 tion, such as tall shrubs and trees, we no- 

 tice the movements of the air less and less. 

 It is a fact that if we pass into the strata 

 of air above the tree tops there is about 

 as much wind in a wooded country as in 



