262 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



we never inquire as to the locality from which our flour comes 

 or the conditions of moisture under which the wheat is grown? 



Some of our investigations in Ohio show that the weather 

 during June of one year has a greater effect upon the apple 

 yield of the next year than the weather of any other month of 

 the next fifteen, but is this universally true? We know something 

 of the effect of longer hours of sunshine or of daylight in varying 

 the color of flowers and the texture of fruit and of grain, but 

 we know little of the effect of much sunshine at just the proper 

 period of growth in producing some extraordinary yields. 



As I see the matter agricultural meteorology can answer 

 these and a multitude of similar questions by finding the critical 

 period of growth for the different plants in different parts of the 

 country and then correlating this knowledge with the known 

 climatic factors. 



The determination of the critical period of the plant and the 

 weather most affecting it can be accomplished in twO' ways. One 

 by a systematic study of the temperature, rainfall, sunshine, and 

 •evaporation at the Agricultural Experiment Stations and the 

 record of the immediate effect of these conditions on the various 

 plants. This is the plan that is in effect in Russia and has just 

 been taken up in Canada. 



The other is by correlating the crop yields during past years 

 with the weather conditions that prevailed during each growing 

 season, by means of charts and correlation tables. To accomplish 

 this the tabulating and charting of climatological data under way 

 by the Weather Bureau must be completed and the average and 

 extreme temperature, rainfall, and sunshine data determined, not 

 only for States but for groups of States and for parts of States. 

 These should cover as many years as possible and be tabulated 

 by months and groups of months. In the most important agri- 

 cultural districts the averages should be determined for lo-day 

 periods or for definite weekly periods. 



THE VALUE OF SUCH A SERVICE 



The United States Weather Bureau is and has been for 

 years carrying on definite work in the interest of agriculture 



