488 KEPORT OF THE SECRETARY OF THE 



far above ours, but upon approacljing Lake Michigan it receives 

 a wonderful downward deflection. This influence extends 

 many miles inward, but upon approaching the center of the 

 State this isotherm rises once more, giviug to the line, as it 

 crosses the State, an arched or convex appearance. In other 

 words, the body of Lake Michigan exerts a wonderful cooling 

 influence on the heat of our lakeside summers; and while 

 furnishing an abundance of warmth to bring to a luscious ma- 

 turity our fruit harvest, yet it is deprived of that fervid aridity 

 so often characteristic of our inland summers. Take, again, 

 the isocheim of our winters, — say 25°. It comes upon us from 

 latitudes far below ours; but on approaching Lake Michigan 

 it receives a wonderful upward inflection, the influence of the 

 lake extending inward some miles ; but this line, on approach- 

 ing the center of our State, begins to sweep downward, thus 

 presenting a slightly saucer-shaped or concave appearance. In 

 other "words, the body of Lake IMichigan exerts upon our lake- 

 side Avinters a powerful influence of warmth, thus depriving 

 them of tlie rigorous and fatal extremes which characterize 

 the season in Central Michigan. Many, doubtless, have wit- 

 nessed the phenomenon described by Judge Ramsdell, on some 

 of our cold and crispy winter mornings, when a dense cloud 

 of vai^or is seen steaming up from the lake, as far as the eye 

 can reach. The great lake is exerting itself, with an almost 

 conscious power, to temper the stinging air; and when we 

 remember that every foot of its 23,000 square miles of surface 

 is at work, we cannot Avonder at the magnitude of the result. 

 This same protecting blanket of watery vapor it is, that the 

 gardener uses on a reduced scale. Has he a choice tree that he 

 desires to guard from the late frosts, he places underneath it a 

 tub of water. Does he wish to protect his early vegetables, he 

 freshly stirs the earth at evening, that the watery vapor arising 

 may envelop each tender shoot in its protecting embrace. 

 This equalizing influence of the great lakes it is, that makes 

 the temperature of the winter, within their influence, almost 



