160 METHODS OF FORECASTING THE WEATHEE. 



the details of the weather attending them; (/>) the deduction of the 

 rules, according to which one form of di.stri])ution of pressure either 

 remains stationary, or moves over Europe, or changes into another 

 form, or is pushed aside by some other type. 



It is in the nature of things that the hrst task is more easily accom- 

 plished than the second. The present state of the art of weather pre- 

 diction in our central meteorological institutes corresponds to this 

 condition of nftairs. The details of the weather conditions within the 

 various styles of pressure distril)ution are, on the whole, quite well 

 known. However, there remains much to be done in this direction, and 

 it is now one of the most important duties of meteorology to most 

 thoroughly investigate, in all directions and details, the distribution 

 of the weather according to the forms of pressure distril)ution. The 

 knowledge of the weather condition^^ for every place and for every 

 type of pressure distribution otiers the only entirely satisfactor}" 

 empirical basis for weather predictions; moreover, it is by this knowl- 

 edge alone that we can hope at some time to discover the fundamental 

 laws of the changes in the weather. This knowledge, however, does not 

 lead us inunediately to a prediction of the approaching weather, but only 

 teaches us to know the weather of one particular place when the distri- 

 bution of pressure is known. In order to he able to predict the weather, 

 we nuist know one thing more — we nuist know in advance what distri- 

 bution of atmospheric pressure will prevail at the time for which we are 

 predicting the weather. This foreknowledge of the pressuredistribution 

 is the starting poi nt upon which the whole weather forecast depends. If 

 this foreknowledge of the future distribution of atmospheric pressure is 

 impossilde, then weather prediction is impossible; if we can foretell it 

 approximately, then a weather prediction of greater' or less probabilit}^ 

 is possil)le, and we shall be al)le to make a larger number of correct 

 than of incorrect predictions; if the distribution of atmospheric pres- 

 sure can be known in advance with certaint}', then we shall be able to 

 make weather predictions with certainty. 



NoAv, how do we stand as to the question of certainty in foreseeing 

 the approaching distribution of atmospheric pressure? If we knew 

 the laws according to which one distribution of atmospheric pressure 

 changes over into another, or according to which it moves across 

 Europe, as well as the laws that cause one distribution of atmospheric 

 pressure to contiiuu^ stationary or suddenly break up and another one 

 result from it, then the problem could be solved and future weather 

 could be predicted with entire certainty. We should proceed with 

 mathematical accuracy in the prediction of weather, and be able to 

 attain the correctness of the astronomers in their predictions of celes- 

 tial planetar}' motions and phenomena. This, of course, is the ultimate 

 aim of meteorological science, but we are at present so far removed 

 from it that we have many well-founded doubts as to whether this 

 object will ever be attained, l^p to the present time we are only able 



