Public Parks. 57 



SOUTH-WEST WIND. 



The prevailing wind, not alone of Chicago, but of the greater por- 

 tion of the valley of the Mississippi, is the south-west. In iS68, it was 

 the hottest and coldest,* and, when great disturbances take place, the 

 same has been observed to occur within the short period of a month. 

 In the summer it is hot, dry and relaxing, causing at first free evapo- 

 ration ; but if long continued, it produces harshness and dryness of 

 the skin, and general malaise ; in w^inter it is dry, cold, and sharp. 

 It partakes of the character of the country, and of the seasons ; the 

 surface being a flat, level plain, with an altitude of only lo feet above 

 the level of the lake at the highest point, necessarily a large portion 

 swampy, with nothing to impede its sweep, plainly showing how it 

 may alternately be the hottest and coldest, even in so short a period 

 as a month. It is the normal wind of the summer and autumn in 

 this latitude, but owing to the local topography, and the great and 

 sudden changes incident thereto, it alternates in frequency, between 

 summer, autumn, and winter. This wind having a greater elabora- 

 ting surface than any other, necessarily exercises a great influence upon 

 health, in addition to its wafting the malarious exhalations of Mud 

 Lake, and the region contiguous to the Illinois and Michigan canal, 

 over every portion of our city, and next to the south-east is the 

 most fatal ; and, owing to its being the most prevalent wind, causes 

 the greatest mortality, f 



* In I867 a very able and interesting memorial was presented to the Michigan Legislature, in 

 obedience to instructions received from the State Board of Agriculture by T. T. Lyon and Sanford 

 Howard, Esqrs., on the change of climate caused by the destruction of the forest trees, and the conse- 

 quent injurious effect upon crops and fruit trees, petitioning the Legislature to enact laws to prevent 

 the unnecessary destruction of the forests, and to encourage the planting of trees, as a means of shelter 

 and protection to crops and fruit trees. In this report they alluded to the change that had taken 

 place in the older portion of the State, within the last thirty years, in the extremes of heat and cold ; 

 the greater prevalence and force of the winds ; resulting in the destruction of peach trees, wheat, com, 

 and the winter killing of clover. The memorial says: " Last year the loss in all that part of the State 

 lying south of the Michigan Central Railroad,-a region deprived of the ameliorating influence of Lake 

 Michigan, or the south-west wind, and composing the richest agricultural portion of the State, was 

 estimated at no less than three-fourths of the entire wheat crop ! From what enquiries your committee 

 have been able to make, the loss on the wheat crop alone, of this State, for the last four years, is not 

 less than §20,000,000. Your committee would be most happy to believe that this enormous loss springs 

 from causes evanescent in their nature, and destined speedily to pass away, to return nevermore. But 

 vour committee are fearful that these vast losses "are but the beginning of sorrow," and that the improv- 

 idence which laid our open fields to that scourge of God, the south-west wind, by the wholesale destruction 

 of our forests, is now only beginning to reap the fruit of that want of forethought, and that these losses 

 can be avoided only by restoring, in part at least, the natural barriers against the wind." 



Diagrams are given showing the influence of the winds on temperature and rain, for four years, at 

 Lansing, clearly demonstrating that the conclusions of the committee were based upon facts. An 

 examination of the topography of the lower and central portions of Michigan will show the cause of 

 the frequency and influence of the south-west wind. The Legislature, with commendable judgment 

 and foresight, passed a .law encouraging the planting of trees and shrubs along the highways, also 

 providing for their care and protection. 



t The effect of this wind on the health of the city, particularly in summer and autumn, will be 

 appreciated, when it is borne in mind that a large extent of the surface over which it passes before 

 reaching the city, is covered by water in the spring, which is evaporated during the sumrner and autumn, 

 leaving the large quantity of humus, or vegetable mould that covers it. exposed to the influence of the 

 sun and air, in addition to liberating a large portion of the carbonic acid that is held by the soil. What 

 makes it still worse, is the fact that but little of the soil for miles in this direction is cultivated. 



