CLIMATE OF THE LAKE SUPERIOR COUNTRY. 469 



east of the Ontonagon, on the 13th of July, such as to kill garden vegetables. 

 The same year (1846), the fall frosts did not occur, so as to freeze Avater, till Octo- 

 ber 5th. Forty and fifty miles south of the Lake, at the sources of the rivers 

 that run to the Mississippi, the weather is represented by all traders to be much 

 more severe and more variable than it is near the coast. The volume of water 

 is so great, as to act in a controlling manner upon the temperature of the sur- 

 rounding country. 



In winter, it does not freeze till late, allowing of navigation in December ; and in 

 summer, it feels the increase of temperature slowly. Off Keweenaw Point, in July 

 last, the surface-water was found to be 37° Fahrenheit. As this is near the degree 

 of greatest density of water, a reason may be assigned why the waves of Lake 

 Superior produce greater effects upon the shore than those of the Lower Lakes, the 

 water being heavier during the summer months. 



The approximate mean of the two warmest months of the summer of 1849, has 

 been given above. It indicates a moderate and delightful summer climate. 



I am able to add the observations of the army surgeons stationed at Fort Wilkins, 

 from June, 1844, to June, 1846, taken from their reports to the Surgeon-General at 

 Washington. 



July, 1844.— Sunrise, 5(377° ; 9 A. M., 64-38° ; 3 p. M., 72-03° ; 9 p. M., 60-03°. 

 August, 1844.— Sunrise, 57-70° ; 9 a.m., 64-19° ; 3 p. u., 69-80° ; 9 p. M., 60-70°. 

 July, 1845.— -Sunrise, 58-0°; 9 a.m., 64-87° ; 3 p. m., 71°; 9 p.m., 61-32°. 

 August, 1845.— Sunrise, 68-48° ; 9 a. m., 62-85°; 3 p. M., 6741° ; 9 p. M., 5748°. 



The greatest range in the morning monthly mean for three years, 1844, '45, '49, 

 is 14°, during the two hottest months of the year. The greatest difference of all 

 the observed monthly means above given, is 18°. 



Without going over all the observations in detail, we may get an idea of the 

 other extreme of the season, by an abstract of the three coldest winter months, 

 taken from the surgeons' report. 



December, 1844.— Sunrise, 20-93° ; 9 A. M., 2245° j 3 r. m., 25-09° ; 9 p. m., 22-22°. 

 January, 1845.— Sunrise, 19-96° ; 9 A. M., 21-70° j 3 p. M., 23-61° ; 9 P. M., 20-32°. 

 February, 1845.— Sunrise, 20-96° ; 9 A. M., 23-03° ; 3 p. M., 28° ; 9 p. m., 22-82°. 



The lowest point in December was 6° above zero, — in January and February, 

 zero. 



December, 1845.— Sunrise, 16-38° ; 9 A. M., 19-06° ; 3 p. m., 20-12° ; 9 p. m., 18-16°. 

 January, 1846.— Sunrise, 23-29° ; 9 A. m., 25-03° ; 3 p. M., 28-74° ; 9 p. m., 24-54°. 

 February, 1846.— Sunrise, 16-35°; 9 A. m., 18-53° ; 3 r. M., 23-32°; 9 p. m., 18-17°. 



In December, the lowest was 4° below zero; in January, 2°; in February, 9° 

 below. The 24th, 25th, and 26th, ranging from zero to — 9°. 



The observations are not continued over a sufficient number of years to fix the 

 average of the climate, but show a much more moderate winter than would be 

 anticipated in latitude 47i° north. The post was evacuated at the beginning of 



