METHODS OF FORECASTING THE WEATHER. 161 



to deduce from the experience hitherto acquired a few empirical laws 

 of limited applica])ility, according to which the types of distril)utioii of 

 atmospheric pressure remain stationary, chanoe, or transform them- 

 selves entirely, or perhaps move away over the earth; even this limited 

 empirical knowledge relates almost entirely to the change from one 

 day to the next. Since these empirical laws as to the changes in the 

 distributioji of atmospheric pressure are so defective the difficulty of 

 foreseeing the approaching distri])ution of pressure is correspondingly 

 great, and the prediction of the weather even for the next day is pro- 

 portionately unreliable. Since we have to do only with theorems 

 founded entirely upon experience, the persons best (pialitied to make 

 the predictions are those who through long years of practice have col- 

 lected the most theorems as to the variations in the forms of pressure 

 distribution, and have also learned by practice the many modifications 

 to which these theorems are subject. In the forecasts for the next day 

 men of much experience attain to more than 80 verifications in a total 

 of lUO predictions; but the prediction of the distribution of pressure 

 for more than one day in advance has such a low probability that in a 

 forecast of the weather for several da3'^s in advance we must expect 

 more failures than results. 



You will say: " It is despairingly little that we have to expect from 

 scientific weather predictions, and hence it is not to be wondered at 

 that the public generally clamors for methods that promise more." 

 It is easy to promise, l)ut one's promise must be kept, and that is 

 difficult. It would also be easy for scientific meteorologists to make 

 the same promises and boastings as the other weather prophets, but 

 they would then cease to be called scientific. And of what use is it 

 to cling to those weather prophets who certainl}^ promise a great 

 deal, but finalh' leave you in the lurch 1 Of the popular methods of 

 predicting the weather above enumerated, none accomplish nearly as 

 much as is accomplished at present by the scientific method; indeed, 

 very often they accomplish nothing beyond the noise they make in 

 praising themselves. However, l)ef ore I begin to criticise the various 

 methods, I will liriefl}' lay before you the processes adopted in weather 

 prediction at the central meteorological stations. You know that at our 

 central office in Vienna, for example, telegrams arrive every morning 

 from more than 1-10 places over the whole of Europe; these t(degi'ams 

 contain the observations made that morning of pressure, temperature, 

 moisture, precipitation, and wind. According to these telegrams the 

 chart of the distribution of atmospheric pressui-e is drawn as it pre- 

 vailed over Europe that morning; and from this particular st3Me of 

 distribution of atmospheric pressure in conjunction with that which 

 prevailed on the preceding day, and by making use of the above- 

 mentioned empirical laws governing the chang(\s in the forms of the 

 pi'essure areas, a tracing is made of the probable areas of atmospheric 



