WASHTENAW COUNTY POMOLOGICAL SOCIETY. 375 



climate of their peninsula could almost be reconstructed from their myths. 

 This interest in the weather there continues unabated, and some of the most 

 eminent living students of the subject are to bo found there. They claim 

 that the results of disforestinor are there entirely unnoteworthy. America is 

 so new that it is not so much a question here as to what has happened as 

 what will result from disforesting and reforesting. The subject has, how- 

 ever, already been much studied, but the conclusions seem various. Dr. 

 Hinrich, the eminent meteorologist of lo'wg,, finds unmistakable evidence 

 that ill his State rainfall lines and forest om lines go together. It has been fre- 

 quently claimed and almost as frequently denied that with the extension of 

 settlement, and with it tree planting on the plains, increased rainfall and 

 amelioration of climate have resulted. The question is not yet settled, but 

 the balance tends to turn to the side of amelioration. Recently Mr. Henry 

 Gauvett has attempted to show that no change of rainfall can be expected 

 from change in forests. 



I have stated as clearly as practicable the variations in conclusions in order 

 to point out that the disagreements are more apparent than real, and that 

 they result from not making a proper distinction — a distinction which I 

 think we have only lately been in a condition to point out. This distinction 

 is to be found in the three different elements of weather or climate. 



One part of our climate or weather is of a general character, due to the 

 inclination of the earth's axis, to the general character of the atmosphere, 

 and, to a less degree, to the general distribution of land and water, 

 mountain and plain over the surface of the earth. A second part of our 

 climate and weather is the periodic, and more especially the daily variation 

 of barometer, of thermometer, of relative moisture, of wind, and of cloudi- 

 ness and precipitation. The source of these changes is to be found in quite 

 as general conditions as the former, but the quantity of the changes is much 

 more dependent on local conditions. The temperature on the average is 

 warmest with us at 2 or 3 P. M., and coldest about 6 A. M., but the range of 

 the change will be very different for different parts of Michigan, and even 

 for different parts of Washtenaw county or of Ann Arbor. 



The third element of our climate is to be found in purely local conditions. 

 Elevation here plays a very important part. The weather of the east side of 

 a mountain range may be very different from that of the west side. The 

 weather of the deep valley may be quite different from that of its limiting 

 ridges. On a still cold day in winter the temperature may change consider- 

 ably with slight changes of elevation. In such weather the thermometer al- 

 ways stand higher at the observatory than in any other part of the city and 

 between the observatory and the Huron river, half a mile north but perhaps 

 100 feet lower, we have frequently noted a difference of 12"^ or 15°. 



Now of these three elements which would be affected most by local forest- 

 ing or disforesting? Evidently not the general element. Our general weather 

 is made up largely of large storm areas or cyclones followed by large quiet, 

 clear areas or anti-cyclones, all traveling eastward with more or less regularity. 

 These areas aie usually first seen in the Rocky mountains or to the east of 

 these mountains. Sometimes they come from the Pacific ocean or from 

 Alaska. Very rarely they appear lo originate nearer home. Their cause of 

 origin and exact source are unknown but we are positive that they depend on 

 general conditions, conditions of the whole earth or of very large areas. For 

 instance two large areas of low barometer usually occupy, one the north 



