x PRACTICAL PURPOSE 283 



accentuated this remark in a speech made at the opening 

 of a Congress of Applied Chemistry in London in 1909. 

 His Majesty said : 



I fully appreciate the important part which chemistry plays 

 in almost every branch of our modern industry. We all recognise 

 that without a scientific foundation no permanent superstructure 

 can be raised. Does not experience warn us that the rule of 

 thumb is dead, and that the rule of science has taken its place, 

 that to-day we cannot be satisfied with the crude methods 

 which were sufficient for our forefathers, and that those great 

 industries which do not keep abreast of the advance of science 

 must surely and rapidly decline ? 



It would be easy to give many examples of the bene- 

 ficial effects of the co-operation of scientific theory with 

 practical methods. One of the most striking illustrations 

 is afforded by the optical trade. About 1863, the firm 

 of Carl Zeiss, of Jena, asked Ernst Abbe to assist them 

 in the development of the microscope by investigating 

 the optical theory of the instrument. Abbe proved 

 mathematically that with the glass then at the optician's 

 disposal no great improvement in the optical parts of 

 the microscope could be expected. Progress in the art 

 of glass-making was necessary before any substantial 

 advance could be made in microscopic or photographic 

 lenses. Abbe himself, with Otto Schott, began, there- 

 fore, in 1881, to investigate the relation between the 

 optical properties and the chemical composition of 

 glasses. When they began their work, about six 

 chemical elements were the constituents of glasses ; 

 and they tested by experiment the effect of adding 

 definite quantities of other substances, as had been done 

 previously in a small way by the Canon W. V. Harcourt 

 in England. 



What had been a rule-of-thumb industry was thus 

 re-constructed on a scientific basis. Glasses could be 



