52 PRESIDENTIAL ADDRESS SECTION B. 



It may be mentioned, as of local personal interest, that Dr. 

 I.iint, of the Cape Observatory, is a chemist turned astronomer, 

 lured first by the connecting link of the spectroscope. Mr. 

 H. E. Wood, of the Johannesburg^ Observatory, one ol our 

 vice-presidents last year, is a physicist turned astronomer. 



As an illustration of the application of Chemistry to 

 Geology, the work of van 't Hoff on the salt deposits at Stass- 

 fort. East Prussia, may be cited. These salt beds, best known 

 from their enormous economic importance as major source of 

 the world's supply of Potash, have been shown, largely by 

 chemico'-geological methods, to have been formed b^^ the 

 gradual drying up of an inland sea, the various salts now found 

 being deposited at varying temperature and concentration in 

 accordance with the laws governing ionic equilibrium in solu- 

 tion. Van 't Hoff, from the elaborate data acquired in his work 

 on the chemical compounds occurring in the Stassfort beds, was 

 able to show that certain of these were only capable of simul- 

 taneous deposition within narrow limits of temperature. Thus 

 from the presence of Glauber's salt and Astrakanite in the same 

 stratum, he could fix the temperature at which that stratum 

 was laid down as between 4.5°C and i8°C. Other sensitive com- 

 pounds defined still narrower limits, in some cases giving upper 

 and lower ranges to within half a degree, and by skilful inter- 

 pretation of chemical data it became possible to determine very 

 accurately the actual temperatures, and nature of seasonal varia- 

 tion, under which the various strata were deposited ; thus afford- 

 ing invaluable information to the geologist concerning con- 

 ditions maintaining millions of years ago. As for the 

 present day, the utihsation of these beds, with their output of 

 thirteen million tons of potash salts per annum, demands the 

 services of the trained chemist at every turn, while the ramifi- 

 cations of the industries dependent upon them brings in highly 

 specialised sections of chemistry in all directions. Their use 

 in agriculture has been associated with the l)udding of ]>ure 

 chemistry into " agricultural chemistry " — in which connection it 

 may be pointed out that far and away the greater ])art of the 

 basic work upon which scientific agriculture turns, is due to 

 chemists and botanists who succumbed to the fission of their 

 sciences. 



The development of Agricultural Science is too long a story to 

 tell here, but the dominant part played by chemists is reflected 

 in the personnel of institutions devoted to agricultural research. 

 At Rothamsted, for instance, the succession of directors has been 

 a succession of able chemists. That, in the opinion of com- 

 petent agricultural authorities, specialisation in applied sciences 

 should still follow the natural cleavage line of fission from the 

 pure sciences, is clearly indicated by the recent " Memorandum 

 on the Reconstruction of Agricultural Education in England 

 and Wales," published by the Agrciultural Education Associa- 

 tion. Paragraph 65 runs : " For the ' scientific specialist ' class 



