70 



Public Parks. 



ature, and the small amount of rain that fell, is marked in the great 

 diminution of deaths in all the months but January and December, 

 as compared with 1866, although a great increase in population 

 had taken place. 



A striking contrast is, however, found in 1868, when the extremes 

 of heat and cold were very marked, with the fall of an unusually 

 large amount of rain. January and February were very cold, March 

 warm, April cold. May warm, and June cold, July and August 

 intensely hot ; and from this time, the temperature gradually low- 

 ered, until the early part of December when it became intensely 

 cold. The increase of mortality this year, compared with 1867, is 

 great, although no epidemic prevailed, clearly demonstrating the 

 influence of temperature and moisture upon health. 



TEMPERATURE. 



The frequent and sudden changes of temperature, at Chicago, are 

 caused more by the winds than any other cause, owing to the open 

 treeless plain upon which it is located, assisted by the evaporation 

 from Lake Michigan. In the northern hemisphei'e the coldest month 

 is January. In some parts of Canada, at Mackinac and Detroit, it is 

 February ; at Fort Snelling and St. Louis, in January. Here the mean 

 temperature is coldest in January, rarely in February ; in thirteen 

 years the temperature was lowest for five years, in January ; five, in 

 February ; and three, in December. The hottest month in most places 

 is July ; in a few, August ; and at sea, it is always August. Here it is 

 generally July, but sometimes it is August ; and the highest tempera- 

 ture for thirteen years, was in June, four ; July, six ; and August, three 

 times. The undulations of teinperature ai'e greatest in the interior of 

 continents, remote from large bodies of water. Here, as well as at 

 Toledo, Detroit, Mackinac and Milwaukee, the range is not as great 

 as in the country south and west. 



From observations made in the outskirts of the city, north, south 

 and west, during the past year, I am satisfied that the range of 

 temperature has increased at least two degrees, since the observations 

 were made at Fort Dearborn, from 1832 to 1836, and that this 

 increase in range is not as great north of the city, as south and west. 

 The range north, for 1868, was 117° ; south, 120° ; west, 121° ; while 

 at 119 Randolph street, it was only 111°. The mean annual temper- 

 ature has also increased about two degi-ees, although the observations 

 made at 119 Randolph street, for the last three years, indicated a 



