DEPARTMENT OF BOTANICAL RESEARCH. 89 



During the past few years the daily work of some 15,000 students and 

 factory operatives has been tabulated. The results lead to the con- 

 clusion that human energy is more closely dependent upon climate than 

 has hitherto been supposed. It also appears that to-day civilization 

 and cUmatic energy bear a surprisingly intimate relation. Further- 

 more, the final analysis of the evidence obtained last year in the 

 Mohave Desert leads more strongly than ever to the conclusion that 

 the climate of the past has been extremely variable and that the 

 variation has consisted essentially of changes in the distribution and 

 number of cyclonic storms. Thus there is reason to think that in the 

 past civilization and climatic energy were as closely associated as now. 



The second important step in the study of climate during the past 

 year arose in part from the work in the Mohave Desert during 1915 

 and in part from the suggestive writings of M. A. Veeder. In the 

 Mohave work the wonderful series of salt lakes and dry basins from 

 Owens Lake to Death Valley emphasized the conclusion set forth in 

 Publication 192, that changes of climate not only are more important 

 and more rapid than has hitherto been supposed, but that there is no 

 break between small variations visible within a single lifetime and the 

 great variations of the glacial period. In other words, there seems to 

 be growing evidence that a study of present climatic variations fur- 

 nishes the key to those of the past. 



The other conclusion from the lakes of the Mohave Desert was that 

 variations in the strength of the wind have been one of the most 

 important factors in producing cUmatic changes. As far back as 1888 

 Veeder suggested that changes in electrical activity of the sun from day 

 to day, as evidenced in the variations of sun-spots, give rise to varia- 

 tions in barometric pressure and thus in winds and rains. This 

 hypothesis in connection with the huge beaches which seem to have 

 been formed in former times by the action of phenomenally strong 

 winds around Owens Lake, for example, led Dr. Huntington to under- 

 take a mathematical analysis of the relation between sun-spots and 

 barometric pressure. Instead of using the actual sun-spot numbers, as 

 has been the almost universal custom, the change in spottedness for 

 each day was computed. A new method was likewise employed to 

 compute the barometric pressure. The problem was to determine the 

 strength of the wind-producing forces. Therefore, instead of using 

 extremes or averages, as is commonly the case, an actual count was 

 made of the number of isobars crossing every fifth degree of latitude 

 and every tenth degree of longitude. 



Both the solar and terrestrial data have been computed for each 

 day for seven years. The two sets of figures have been compared by a 

 method of correlation coefficients. Since the day and month are the 

 units instead of the month and year as in most investigations, a period 

 of seven years gives results of comparatively high accuracy. There 



