22 PRESTDEXTIAL ADDRESS SFXTIOX A. 



In tliis case in summer we maj forecast extensive rains inland. 

 A third common type is the one I have alluded to before. A \'- 

 shaped depression appears in the south-west, and graduallv 

 sweeps over Soutli vVfrica from West to East, with a line of 

 duststorms in winter and thunderstorms in summer. 



Examples might be multiplied indeimitely. These are, I 

 think, sufficient to show, that although weather forecasting is 

 based on a sound, scientific basis, it is in practice an affair of 

 experience supplemented by that inborn and hardly-acquired gift 

 which in doctors is called the gift of right diagnosis. We may 

 say that, as far as weather ])redictions are concerned, 

 meteorology is in the position in wdiich medicine was before 

 Pasteur. The wonderful progress of physiology, chemistry, and 

 other sciences in the first half of the nineteenth century had put 

 medicine on a sound, scientific basis. The ailments we are sub- 

 jected to had been carefully studied and described in their various 

 phases, but when it came to ])ractice it was found that after all 

 a doctor, however well grou.nded in general knowledge, had to 

 rely mainly on experience, and had to trust a great deal to his gift 

 of intuition. By the discoveries of Pasteur, medicine has made 

 enormous strides forward ; it has certainties now where before 

 it had only probabilities, and in many cases can point to 90 and 

 even 90 per cent, of successes, when before the proportion was 

 often reversed. Will meteorology ever find a solution to this 

 problem of the transformation of pressure systems, which, as far 

 as meteorology is a ])ractical science, constitutes its chief end? 

 Some have hopes that the solution is not far oft', and that 

 generations to come will find it hard to understand how we could 

 live comfortably without ever being certain of the weather of the 

 morrow. Others are not so sanguine. Professor Pernter. in an 

 address to the Austrian Association for the Advancement of 

 Scientific Knowledge some years ago, said : 



" To predict the weather with certainty is the uhimate aim of 

 meteorological science, Init we arc at present so far removed from it 

 that we have many well-fonnde'l doulits as to vvhetlicr this object will 

 ever be attained.'' 



In spite of the difiiculties inherent in this part of meteorology, 

 the various weather bureaux are fairly successful in their weather 

 forecasts. Their successes vary from 80 to 90 per cent. In some 

 cases they are even more successful. The American Weather 

 Bureati, for instance, can boast that for years no storm struck the 

 East Coast of the States without timely warning of its approach 

 having been given, and — what in some respects is even more im- 

 portant — that for several }'ears no wrong warnings have been 

 given, every storm they had predicted having been courteotis 

 enough to keep the appointment. 



A new method of weather forecasting has been brought 

 forward within the last few years, and has attracted a great denl 

 of attention. It has its opponents and its sympathisers in 

 meteorological circles. It rests on principles that are most of 



