118 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



that I had at times to predict no rain, when with identical condi- 

 tions as shown by the weather map I should in a wet winter have 

 predicted a widespread fall. Even in England, in winter, there 

 is an appreciable persistence in the characteristics: During the last 

 60 years the 15 wettest Januarys were followed by Februarys of 

 more than average rainfall in 10 cases ; and with dry Januarys also 

 there is a similar two-to-one chance of a prolongation of the char- 

 acter. It is this persistence, especially when it is preceded by 

 abnormal features in other regions, that seems now to hold out most 

 promise of reliability in forecasting. In agricultural countries in 

 which a failure of the rains involves a national calamity, the desir- 

 ability of making preparations in advance has long ago led to efforts 

 at prediction ; and the demand has been so great that the supply has 

 been forthcoming before its quality would bear the most cursory 

 examination. The causes of unusual weather seem hopelessly ob- 

 scure to the layman; and hence primitive ideas, surviving in the 

 depth of our natures from countless ages of magical practices, still 

 come to the surface in connection with it. In India I have been 

 officially asked what is the need of an expensive and difficult scien- 

 tific inquiry into the causes of drought when Hindu astrology will 

 indicate what is coming ; and many a country that claims to be dom- 

 inated by western science fails to recognize that events in weather 

 obey the ordinary laws of physics and chemistry. The almost uni- 

 versal idea that weather must repeat itself after a certain number 

 of years finds its origin, I believe, ultimately in the ancient belief in 

 the control of our affairs by the heavenly bodies with their definite 

 cycles — a belief which clearly shows itself in the supposed influence 

 of the moon on the weather. Be that as it may, the faith in periods 

 is so deep-seated that even in scientific discussions the ordinary tests 

 for validity are very often ignored: More than once I have seen in 

 journals of repute the artless remark of an author that if he were 

 to limit his results to those which would satisfy the criteria of reality 

 he would obtain few results of interest. 



Another regrettable feature of current practice, even in important 

 memoirs, is that of classing together processes with true periods and 

 those sometimes called " quasi-periodic ", of which the period varies. 

 If our ideas are to be applied with success in the present enterprise 

 their currency must be stabilized, and no good can come of attempt- 

 ing to pass off a vague surge of a few years as a 3-year period. 



After these preliminary remarks I propose to make a rapid sketch 

 of the relationships that have been found between seasonal features 

 in different parts of the world, then to describe the efforts that have 

 actually been made to issue long-range forecasts, and finally to 

 consider the directions from which improvements can be hoped for. 



