PRFvSIDriXTIAT. ADDKlrlSS SICCTIOX A. 2^ 



tliem new either in substance or in form, and certainly new in the 

 way in which they are ajipliecl. it cannot be passed over now, 

 for if it be proved correct, it will certainly be the most important 

 step forward which meteorology has made within the last fifty 

 years. ."^ix years ago the Belgian [Meteorological Societv 

 organised an international forecasting competition, and oft'ered 

 a substantial prize to any scientist who could bring some notable 

 improvement to the methods then in use for weather predictions. 

 The conditions imposed by the Society were such as to exclude 

 all weather quacks, for the question was practically restricted to 

 tlie following: Predict from given weather charts the barometric 

 variations over the whole of Europe for the next twenty-four 

 hours, the path of the depressions, the birth and dislocation of 

 cyclones and anticyclones. The candidates had besides to write 

 a memoir explaining their method of forecasting. Some of the 

 leading meteorologists of the day, Lawrence Rotch, Teisserenc 

 de Bort, Dr. Polis. Professor B.runhes, consented to be on the 

 Board of Examiners. The jury unanimously awarded the prize 

 to ]\lr. Gabriel Guilbert. the secretary of the IVIeteorological 

 ."Society of Caen in Normandy, because, as Professor Brunhes 

 ]iointed out in his report : 



■' The method this gentleman employs enables him to foresee with 

 precision the displacement and variations for the centres of high and 

 low pressures over Europe. Although this method does not give us 

 an absolute certainty, it has been efficient in forecasting complete trans- 

 formations which no other method so far has been able to predict." 



I'rofessor Brunhes has since taken u]) this question theoreti- 

 cally, and shown that this method was in accordance with the 

 theory of vortices as expounded by Helmholtz, Kelvin, and 

 Bjerknes. He even confirmed his deductions by a series of very 

 neat laboratory experiments. 



I can give only a brief outline of the method. The funda- 

 mental idea is that the surface winds alone have a d'ecisive in- 

 fiuence on the variations of barometric pressure. Neither 

 temperatures, nor areas of precipitation, nor geographical 

 configurations, have to be taken into account. The chief points 

 to be considered on a weather map for predicting pressure 

 variations for tbe next twenty-fotir hours are those where the 

 winds are " abnormal." To grasp the method we must consider 

 what the author understands by abnonual winds. We have seen 

 already that there is a normal systeiu of wind circulation round 

 tlie areas of high or low pressures. Considering the northern 

 hemisphere only, since the author has so far applied his theory 

 to European weather only, we have, if we go from west to east 

 through the south round a cyclonic area, the following sequence: 

 North-west Avinds in the rear, then west, south-west, south and 

 south-east in the front. In an anticyclone the sequence would 

 be reversed : w^e would start with south-east in the rear, to end 

 with north-west in the front after passing through south, south- 



