PRKSIDEXTIAr. ADDRESS SECTION A. 



15 



Section A.— ASTRONOMY. MATHEMATICS. PHYSICS. 

 METEOROLOGY, GEODESY, SURVEYING, ENGI- 

 NEERING, ARCHITECTURE. AND GEOGRAPHY ^ 



V 



/ 



President of the Section. — Rf;v. E. Goetz. S-T-. M.XS^ 



F.R.A.S. /^^ 



WEDNESDAY, JULY ^. 



The President delivered the following address : — "'"^s^ 



WEATHER FORECASTING. 



L should have liked to give you a presidential address on the 

 Meteorology of Rhodesia. But you have given us such short 

 notice of your desire to hold your ninth Annual Meeting in 

 Bulawayo that I have not been able to get through the amount 

 of material work such a paper ])resupposes. I have, therefore, 

 chosen a subject of more general interest, that of Weather Fore- 

 casting. This subject has, besides, a certain actuality. The 

 Transvaal Meteorological Department has had a forecasting 

 service for some years, and its success shows that this service 

 should now be extended to the rest of South Africa. 



It may be said that it was only during the second half of last 

 century that the art of forecasting the weather, an art apparently 

 as old as the world, was put on a scientific basis, when the close 

 connection between the distribution of pressure over large areas 

 and the weather in general was established as an undoubted fact. 

 This connection had been suspected long before, and as far back 

 as 1780 Lavoisier tried to establish a kind of meteorological 

 service, based chiefly on the simultaneous observation of pres- 

 sure at places as far apart as possible. This idea was taken up 

 about the same time in a more systematic way by the Mannheim 

 Meteorological Society, the oldest of all such societies, and a 

 vast amount of data was collected by its members and others all 

 over the west and centre of Europe. These attempts were not. 

 however, successful owing partly to the disturbed state of the 

 political world at the end of the eighteenth and the beginning 

 of the nineteenth centuries, but chiefly, no doubt, to the lack of 

 the rapid system of communication which the invention of the 

 telegraph was to give us half a century later. From the twelve 

 folio volumes of the Mannheim Society's Proceedings. W. H. 

 Brandes. in 1820, extracted the data for a discussion of the 

 weather day by day over Western Europe for the year 1783. 

 This work of Brandes may be considered as the dawn of modern 

 meteorology. He constructed weather maps for successive days, 

 maps which he did not publish, but which may be reconstructed 

 from the data he gives for them, and their discussion led him to 

 the following conclusions : The wind direction is determined by 



