Vn - PERIODIC SEEDING 



NEW MEXICO WORK 



Ey this time, a rather close liaison had been established with Dr. 

 Workman and his co-workers at the New Mexico School of Mines. So, 

 in view of the significance of Langmuir 's analysis of the effects and 

 possibilities of silver-iodide ground seeding, and in order to test as 

 soon as possible his ideas on periodic seeding, a schedule of operations 

 on this basis was estiblished without further ado at New Mexico. 



Starting in December, 1949, a silver-iodide ground-based gener- 

 ator was operated in New Mexico by the project on a schedule so planned 

 as to introduce, if possible, a seven-day periodicity into the weather 

 cycles of the nation. This schedule of regular weekly periodic seedings 

 used about 1000 grams of silver iodide per week, and it continued with 

 a few modifications until the middle of 1951. 



Data were gathered by Falconer, and almost immediately Langmuir 

 found evidences of a definite weekly periodicity in rainfall in the Ohio 

 River Easin. Again, he conducted an exhaustive analysis of the facts and 

 performed elaborate mathematical calculations to determine the prob- 

 abilities that these variations in weather could have taken place by pure 

 chance. 



He reported his findings and his conclusions to the National Academy 

 of Sciences, October 12, 1950 to the American Meteorological Society of 

 New York City on January 30, 195V 25 ) and also to the New York Academy 

 of Sciences on October 23, 195 1.( 24 ) He pointed out that, during 1950, 

 there was a marked and statistically highly significant seven-day perio- 

 dicity in many weather elements. The significance was so high, said he, 

 that it could not be explained on the basis of chance; it could not have 

 occurred anyway from natural causes. It involved not only rainfall but 

 also pressure, humidities, cloudiness, and temperatures over much of 

 the United States. 



said: 



In his paper to the New York Academy of Sciences,' Langmuir 



"Almost immediately, that is, during December 1949 and 

 January 1950, it was noted that the rainfall in the Ohio River 

 Easin began to show a definite weekly periodicity. A conven- 

 ient way of measuring the degree of periodicity was to calcu- 

 late the correlation coefficient CC between the rainfall on the 

 successive days during a 28 -day period, with the sine or the 

 cosine of the time expressed as fractions of a week, the phase 

 being taken to be on Sundays . 



