WASHTENAW COUNTY POMOLOGICAL SOCIETY. 377 



also, the uniformity and p3rsistence of forest streams, No one can under- 

 stand what the latter means unless he has stood on the banks of a stream on 

 the plains or in the treeless part of the Rocky Mountains during a rain 

 higher up the valley- The bed of the stream is dry ; a rushing sound causes 

 the observer to look up the stream; the rain which has just fallen is coming 

 down with a rush; it passes rapidly and in a few hours or at most a few days 

 the stream is again dry. Compare this with the perennial streams of our own 

 woodlands which fed by springs protected by trees, continue almost unchanged 

 from season to season and from year to year. Moreover this sudden rush of 

 water brings with it, in a region recently disforested where the grouni is not 

 yet protected by sod, an immense amount of silt, sand, gravel, and rock, 

 which spread over and ruin the cultivated fields further down. These are the 

 most familiar parts played by forests and are known to all thoughtful men, 

 I mention them here to point out that they are features of local rather than 

 general character, but that they are local does not render them limited in area 

 or unimportant in character. 



But the next feature to which I wish to call your attention ia less familiar 

 to the general public, and also, unfortunately, less completely worked out 

 by professed students of the subject. The features of weather and climate, 

 especially those of summer weather which most interest and affect those who 

 draw their support directly from the soil, are due more to what are called " local 

 storms," than to general storms. A good illustration of these storms is the 

 sharp, quick summer thunderstorm, and the no less sharp and quick, but 

 much more destructive first cousin of the thunderstorm, the tornado. These 

 phenomena are not integral parts of a cyclone or storm area, bat are only 

 indirectly connected with it. They are generally connected with some un- 

 symmetrical feature of a cyclone,* such as an arm put out to southward, or a 

 brood of small secondary whirls like a hen with her brood of chicks. To these 

 local storms the most of our summer rains are due, and in some parts of the 

 world all rainfall comes from them. These are the phenomena too, which 

 the weather-predicter in his central bureau at Washington or Toronto or 

 London is least able to foresee. These storms generally run low and are, 

 therefore, especially sensitive to local conditions. The hail comes from them, 

 and thus we find in France the fact that hail storms are somewhat guided by 

 the outlines of forests, as they lie low they will be more likely to be influenced 

 by moisture preserved by forests, and the increased rainfall in or near forests 

 is probably much more due to them than to an increase in intensity in the 

 general cyclone. 



But the action of forests on these local storms is by no means clear, and it is 

 here that there is an opportunity for profitable study for every intelligent 

 observer' of nature. It seems that some kinds of local storms maybe in- 

 creased in intensity by the presence of forests. So far as that increase is 

 rainfall it is favorable for Michigan, for a cloudburst in a forest need not re- 

 sult in a flood in the adjacent streams as it would necessarily result in open 

 land. And may I be pardoned for calling attention to this line of study of 

 local storms and local influences? The study of the general weather is cared 

 for by the general government and by professed meteorologists. The local 

 conditions are however of the greatest importance, and this should be cared 



* The cyclone is an area of general low barometer and its name is due to the circulation of wind 

 in it. Its individual character may vary from so slight an iatensity that it is barely recognized by 

 instruments and not at all by the senses, to as great an intensity as that of the West Indian hurri- 

 cane. The tornado is a small whirlwind of great intensity, but is not a cyclone. 



