President's Address. v 



differences of constitution. A well-known example is that of 

 Moscow, standing on a plain which underneath has a density 

 much smaller than one would expect. The anomaly is due to the 

 presence of a great coalfield. 



I have now stated to you how the subjects of meteorology, earth 

 magnetism, and gravitation are related to each other. You will now 

 understand how it is that the study of meteorology is incomplete 

 without a simultaneous study of the daily and annual variations of 

 earth magnetism and of atmospheric electricity, and how the 

 geologist's knowledge of the constitution of the earth's crust must 

 be supplemented by a study of magnetic and of gravitational 

 anomalies. 



I come now more particularly to consider what we in South 

 Africa have done for the study of these subjects, and whether 

 what we have done is sufficient to give us all the information we 

 desire. You will have noticed that the deductions from any survey 

 can be drawn only after corrections have been applied to eliminate 

 the effect of known causes such as the sun's heat and the shape of 

 the earth, and in the case of earth magnetism allowance has been 

 made for the secular variation. A lack of knowledge of these cor- 

 rections would lead us to make wrong deductions, and the first 

 essential is the establishment of a well equipped central station 

 where continuous records of the phenomena may be taken. After 

 that it would be necessary to establish one or two subsidiary 

 stations for usually a short period to take continuous records at 

 other properly chosen places. It would then be possible to make 

 surveys of the country and correct the results for the deviations I 

 have spoken of. 



At present there is a station in the Transvaal purely meteorolo- 

 gical. De Beers have at Kimberley a meteorological station whence 

 Mr. Sutton has issued a number of papers which constitute a most 

 valuable contribution to South African Meteorology. 



The Imperial Government had a very complete station at the 

 Royal Observatory in which meteorological and magnetical observa- 

 tions were taken for a number of years between 1840 and 1850. 

 What knowledge we have of the daily and the annual variations of 

 the meteorological and the magnetic elements for this part of the 

 Colony is derived from observations taken there. 



The Cape Colony has never supported such a station, which is a 

 matter for wonder, because science is seldom received unsympatheti- 

 cally, unless the financial state is bad, and since the demise of the 

 Imperial Government's station there have been several occasions on 

 which the Government had money to spend. Again, Cape Colony 



