STUDIES IN LAKE AND STREAMSIDE VEGETATION 



141 



month of about 15 degrees Fahrenheit in the two stations. Since the 

 altitudinal difference is about 4,700 feet (1,430 meters) this means an 

 average depression of temperature of 3.2 degrees F. for each 1,000 

 feet (6.5 degrees C. for each 1,000 meters) of altitude. 1 A comparison 

 of the records of the observer at Idaho Springs, Colo., which is 40 km. 



Fig. 6. — Graphic Representation of the Mean Temperature by Months at 

 Phoenix, Ariz., St. Louis, Mo., Boulder, Colo., Duluth, Minn., and Redrock: 

 Lake, Colo. 



Particularly noticeable is the low summer temperature at Redrock Lake. In con- 

 nection with this figure the reader should consult Table II. A description of the method 

 employed in preparing the Redrock Lake curve is given in the text. 



(25 miles) south of Redrock Lake, but at a lower altitude, shows a 

 difference of about 10 degrees F. for the summer months of 1908. The 



1 The observations of De Saussure in the Alps showed a depression of about 6.3 degrees C. for each 

 1,000 meters. Hence conditions at Redrock Lake may be taken as quite normal for mountain regions. De Saus- 

 sure's figures, together with others from various investigators in different parts of the world, are given by Hann, 

 pp. 243-45. (See the following note.) 



