WEATHER BUREAU. 61 



preliminary to cooperation to determine the critical period of crops 

 and the weather that has the greatest effect on crop yields, as well as 

 on the extent of insect and fungous damage. It is expected that a 

 definite and extensive system for keeping regular records of the differ- 

 ent weather factors and the development of the most important 

 crops will be instituted at a large number of these stations, and such 

 preliminary work started as may be continued through a series of 

 years, and from which large results may be anticipated. 



WEATHER AND CROP STUDIES. 



The chief of this division, before his appointment to this position, 

 had made studies to determine the critical period of growth of corn, 

 potatoes, wheat, hay. fruit, and other crops by mathematical and 

 graphical correlation methods, and the division is now continuing 

 these studies as fast as the routine duties will allow. Some of the 

 results of these investigations are appearing in the National Weather 

 and Crop Bulletin that is prepared by this division and others will 

 appear from time to time in various publications as the subject is 

 developed. It is believed that it has remarkable possibilities for 

 development for the benefit of the agricultural interests of the 

 country. 



NATIONAL WEATHER AND CROP BULLETIN. 



The most important routine work of the division is the issue of 

 the AVeather and Crop Bulletin, which is published weekly during 

 the summer months and monthly during the winter season/ During 

 the past year publication of the weather and crop diagram pages 

 covering the weather and condition of cotton, corn, and wheat, 

 started in 1915, was continued, but a change was made to allow 

 the division of this territory into 12 diagrams instead of 7, thus 

 making the areas smaller and the data more definite. Detailed 

 studies have been printed to show the effect of rainfall and tempera- 

 ture upon crop conditions, and the knowledge gained in these and 

 other similar studies has been applied in discussing the effect of cur- 

 rent weather upon the development of crops. The regular publication 

 of the Aveekly weather forecasts in the bulletin was discontinued in 

 the spring of 1916, and since then any reference made therein to the 

 forecasts has been in connection with the current weather conditions. 

 The issue of this bulletin is 3,750 copies. 



METEOROLOGICAL RECORDS AND PUBLICATIONS. 



The several annual, monthly, and other serial publications of the 

 bureau have been issued in regular sequence, and continue to supply 

 the general and technical public with useful information. 



On account of the large demands for climatic data from all por- 

 tions of the country, it has been necessary to reprint several of the 

 separate parts of Bulletin W and Climatological Data of the United 

 States by Sections. Others are now ready for reprinting when 

 opportunity offers. The growing demand for these summaries 

 indicates that the entire set should be brought down to date and 

 reprinted. 



