224 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 10 



In accordance with this law the country-wide average rates of var- 

 iation in time, temperature, and distance, as related to periodical 

 phenomena, geographical distribution, range and Hmits of zones, etc., 

 are represented by the unit constants of 4 days to each equivalent 

 constant of 1 degree of latitude, 5 degrees of longitude (or 1 degree 

 isophane), 400 feet of altitude and 1 degree F. of the thermal mean. 

 These unit constants are equivalent, one to the other, and, there- 

 fore, the terms of one unit may be converted into those of another as 

 required in the computation and expression of results. 



The application of the law to the study of any problem relating to 

 life or climate in which the elements and data are subject to expression 

 in terms of quantity, as to time, temperature, and distance, falls 

 within the category of a mathematical concept of variable nature 

 and, therefore, in the solving of bioclimatic problems, involves the 

 determination of certain evidence and facts by mathematical methods. 



Principles involved in the application of the law. — In this mathe- 

 matical concept of the bioclimatic responses to the solar and other 

 fundamental factors of control there are a number of basic principles, 

 namely : 



1. The principle of geographical unit constants which relates to rates 

 of variation or gradients of time, temperature, and distance, with 

 variations in geographical position. 



2. The principle of the isophane and altitude in which the isophane 

 is an expression of the combined unit constant of the latitude and 

 longitude coordinates while the altitude unit constant is a measure 

 of variation with elevation of a place above its sea-level isophane in 

 terms of time, and equivalent units of feet, meters, thermal mean, 

 etc. This principle is fundamental in the systems and methods of 

 application of the law, because it serves to locate and designate a 

 geographical position and to fix its unit value relative to another posi- 

 tion designated as the base. 



3. The principle of the sea-level constant. This represents a uniform 

 element of the system of computation of tables of altitude, time or 

 thermal constants in accordance with the unit constants of the law. 

 Thus, the isophanes of a map or a table, unless otherwise designated, 

 represent a sea-level base and all computations for altitude positions, 

 unless otherwise mentioned, are to or from this base. 



4. The principle of the base station and base data. This principle, 

 in connection with that of the sea-level constant, serves as a central 

 or basic element of a uniform system of computation and comparison 



