HOPKINS: BIOCUMATIC LAW 35 



For a time the study related to plants alone and thus was 

 associated with botany. Later, animals, and still later, the rela- 

 tion of periodical phenomena of plants and animals to climate, 

 were included, and from the first, variation in the time of occur- 

 rence of periodical phenomena with geographical position was 

 recognized. Thus the science is founded on and embraces certain 

 features of biology, climatology, and geography, and involves, 

 in the consideration of its problems, a number of other branches 

 of science and practice. 



Beginning about 1830, special attention was given by German 

 writers to a study, first of the rate of variation with latitude, 

 and later to the variation with altitude, and finally, in 1893, the 

 discovery was announced of a rate of variation with longitude. 



In 1894 the writer noted that the dates of emergence of the 

 periodical cicada in West Virginia varied with the latitude and 

 altitude. This, in connection with the announcement by Dr. 

 Merriam of the relation of cUmate and temperature to the defin- 

 ing of equal or similar biological associations, designated as life 

 zones, led to a consideration of the relation within the State of 

 West Virginia of insect and plant distribution to periodical activ- 

 ities, temperature, latitude, and altitude. About this time the 

 Hessian fly was very destructive to wheat throughout the State 

 and, guided by the findings of Professor Webster that in Ohio there 

 was a difference in safe dates to sow wheat to avoid damage by 

 this insect, varying with latitude north and south of Wostor, 

 an effort was made by the writer to apply the principle in West 

 Virginia. It was soon found that altitude was equally as im- 

 portant as latitude, and a detailed study of this new phase of 

 the problem, aided by phenological observations at different 

 latitudes and altitudes, resulted in the publication in 1895 of 

 Bulletin 67 of the West Virginia University, Agricultural Experi- 

 ment Station, in which it was suggested that the rate of varia- 

 tion in the safe dates for seeding wheat was about one day for 

 fifteen minutes of latitude and one hundred feet of altitude. It 

 was further suggested that this rate of variation was in accord- 

 ance with natural law, which could be applied in designating the 

 time of periodical events or practice for any given place in the 



