THE EFFECT OF CLIMATE AND WEATHER 305 



of clothing, housing and diet is one where the summer 

 months are close to the physical optimum and average 

 about 6^° with daily maxima of 70° to 75° and night tem- 

 peratures of ^s° to 60°, while the winters approach the 

 mental optimum with midday temperatures of 45° to 50° 

 and mild frosts at night. London and the southern end of 

 Puget Sound approach this as closely as almost any places; 

 Oakland in Cahfornia, Santiago in Chile, WelHngton in 

 New Zealand, and the Austrahan seacoast south of Mel- 

 bourne also come near to it, although a httle too warm in 

 winter. But not even London or Puget Sound has an ideal 

 chmate, for other factors as well as temperature must be 

 considered. 



2. Humidity. In attempting to determine the optimum 

 humidity it is essential to employ a method such that the 

 overwhelming effect of temperature does not hide the 

 effect of humidity. One excellent way is by means of climo- 

 graphs. A climograph is one form of what I have called an 

 isograph, which is a general name for a kind of diagram in 

 which two variables are represented by the horizontal 

 and vertical ordinates and a third by isopleths or lines 

 representing equal degrees of intensity. A contour map is a 

 familiar kind of isograph. On such a map one variable is 

 latitude which we measure up and down, or along the 

 vertical ordinates as the mathematician puts it; another 

 is longitude which we measure east and west, or along the 

 horizontal ordinate; the third is altitude which were represent 

 by sinuous contour lines. All points along the coastline 

 are at sea level, or on the zero contour; all points a thousand 

 feet above sea level lie along the thousand-foot contour, 

 and so on until a small area of the highest land may be enclosed 

 by the twenty-thousand-foot contour hne. By coloring the 

 space between sea level and the thousand-foot contour dark 

 green, the space between the thousand- and two thousand- 

 foot lines pale green, and so on with different shades up to 

 dark brown for high altitude, we get a map which gives a 

 general picture of the height of the land. 



A climograph is simply another form of isograph. In the 

 one given in Figure 2 latitude is replaced by temperature, 

 longitude by relative humidity, and height above sea by the 



