226 ABBOT: SOLAR RADIATION MEASUREMENTS 



The tone wheel has, therefore, all the advantages of the latter 

 in keeping out interference and static. In fact, it seems some- 

 what superior in keeping out strong interference. 



(3) It may be used either with radio or audio frequency am- 

 pUfiers. Radio frequency amplification is in general to be pre- 

 ferred on account of possible induction and brush noise. 



(4) While less adaptable to wave length changing than the 

 vacuum tube, this could be accomplished for predetermined wave 

 lengths by a set of automatic speed regulators. 



(5) The brush action would probably be improved by filling in 

 the spaces between the teeth of the wheel with insulating ma- 

 terial so as to present a smooth surface to the brush. 



METEOROLOGY. — The use of solar radiation measurements for 

 weather forecasting in Argentina.^ C. G. Abbot, Smithson- 

 ian Institution. 



Mr. H. H. Clayton, the well-known American meteorologist 

 now in. charge of the forecast division of the Meteorological 

 Service of Argentina, has employed solar radiation observations 

 for more than a year as a forecasting element. I am not in- 

 formed as to the precise details of his methods. In a conversa- 

 tion I held with him in June, 19 19, at La Quiaca, Argentina, he 

 told me that he has maintained for years an impartial quanti- 

 tative mathematical record of both the success and failure of the 

 Argentine official weather forecasts, and that this record showed 

 marked and considerable gain in forecasting from the time of 

 the introduction of this new element. He stated to me quan- 

 titatively the results before and after this event, but as I do 

 not fully understand his system of accounting, I will not venture 

 to repeat them. 



This new departure rests on the fact that our sun is a variable 

 star. This result was reached by the Smithsonian Institution 

 in its investigations of the intensity of solar radiation. For 

 nearly 15 years the Smithsonian Astrophysical Observatory has 

 maintained a solar radiation observing station at Mount Wil- 



' Presented before the Washington Academy of Sciences on January 29, 1920. 



