ECOLOGY OF ISLE ROY ALE. 



41 



valleys. The absence, residual, or organic character of the soil is also 

 an important factor of the environment. 



3. The Atmospheric Influences- and their Evolution, a. Climate. 

 Unfortunately there has been no continuous series of climatological 

 records made on Isle Royale. A few records were made by our party with 

 instruments loaned by Mr. C. F. Schneider of the Michigan Weather 

 Sendee, that, while very imperfect, are suggestive. The mean tempera- 

 ture for 26 days in July is 58° P., the minimum record is 46°, and 

 the "maximum 79°. Prom August 2 to 17 the mean is 59°; the meau 

 maximum is 71° and the mean minimum is 47°. Por the same period 

 the maximum is. 80° and the minimum 36°. There was but little rain 

 although it rained all day on July 15. 



Very fortunately, however, these meager records may be supple- 

 mented by those from Port Arthur, about 25 miles distant on the 

 Canadian shore.^ This data has been kindly furnished by Mr. B. C. 

 Webber of the Canadian Meteorological Service. The records cover the 

 decade of 1896 to 1905, arid show the mean monthly and annual tem- 

 peratures, maximum and minimum temperatures, and the precipitation 

 for the same period. 



The table of temperature. Table 1, shows that the decade average of 

 the mean monthly temperatures for February is 7.65° P., with a maxi- 

 mum during July of 62.24° and an average annual of 36.07°. The 

 monthly averages of the maximum temperatures for January is 38.1° 

 and for July 85.8°, with an average annual of 36.7°. The lowest 

 average monthly temperature for the same period is — 27.5° for ^January, 

 and for July 42.0°. The average minimum temperature for this ten 

 years is — 30.8°. The monthly averages for 5 months are below zero. 



TABLE NO. 1.— MEAN, MONTHLY AND ANNUAL TEMPERATURES AND AVERAGES 

 FOR 10 YEARS. PORT ARTHUR, 1896-1905. 



Mean Temperatures in "F. 



1 For'a general account of the Canadian climate see Stupart '98 and '05, 

 6 



