154 METHODS OF FORECASTING THE WEATHER. 



there is a certain regularity in the recurrence of years with similar 

 characteristics, and that they were justified in enunciating the law^ that 

 almost exactly the same weather returns at intervals of eleven, or of 

 eighteen, or nineteen 3"ears, so that it would onl}" be necessary to 

 expect in the coming year the weather observed a certain lumiber of 

 3^ears before. It is evident that this would be the simplest method 

 for predicting the weather in any year, day by day, or at least week 

 by week, and this is the system followed in the so-called '*hundred- 

 3^ear calendar." Unfortunately the facts do not agree with the 

 predictions. 



Both the methods above named in general endeavor to keep one free 

 from preconceived ideas as to causes, and base their predictions of the 

 weather only upon earlier observations and experience, often sup- 

 ported by records of the weather actually prtn'ailing, whether made 

 with or without instruments. There are other prophets who have 

 sought for the cause that dominates the weather and weather changes 

 and adopting this when found Iiave made their weather predictions 

 in accordance w'ith the properties, movements, and changes of this 

 accepted cause. 



This latter class, somewhat precipitately and without sufficient 

 experience in the principles of observational work, l)ut driven by the 

 innate longing in the human })reast to seek for a cause for all matters 

 and supported only b}' general a priori considerations has sought for 

 the dominating cause of the weather. Thus, from the consideration 

 that the sun dominates everything on the earth, Professor Zenger has 

 chosen that as the agent of the weather changes, which he ascribes to 

 the rotation of the sun on its axis. Now, since the time required for 

 a revolution of the sun occupies al)out twenty-six days, he has chosen 

 one-half of the time of a revolution, that is to say twelve to thir- 

 teen da3's, as the ]:>eriod by which he measures the changes of the 

 weather, and has arranged a weather calendar according to which 

 there is a day of disturbance every twelve to thirteen days. In the 

 interval ])etween the two da3^s of disturbance there is an interval of 

 safety, or what he calls " calms." The comparison of the predictions 

 of the "da^'s of disturbance" and ""da^ys of calms" with the weather 

 actually occurring is supposed to give the proof of the correctness of 

 the assumption that the semirotation of the sun governs the weather. 

 Up to the present time, however, this has not yet been accomplished, 

 for the attempted demonstration lias entirelj^ failed. 



The method of weather predictions proposed by Professor Servus 

 is of a similar character; he considers the interior of the earth, and 

 from the fact that the attraction of the earth upon the atmosphere 

 attaches the latter to the earth, he argues that " all the great disturb- 

 ances in the equilibrium of our atmosphere are caused by changes in 

 the condition of the interior of the earth, which produce disturbances 



