152 



SCIENTIFIC THOUGHT. 



In the mean time this view had gained great support 

 by the efforts of quite a different section of scientific 

 workers, wliose labours had opened out a new and 

 promising field of research. The new field for a con- 

 siderable period belonged almost as exclusively to foreign 

 science as the energy- conception had for twenty years 

 belonged to this country. Early and for the most 

 part isolated labourers were Kopp and Hess in Germany, 

 Eesnault and Berthelot in France, Julius Thomsen in 

 Copenhagen.^ They (with many younger men) can be 



statements. These two forms were 

 the impossibiHty of a perpetual 

 motion and the equality of action 

 and reaction. See his Faraday 

 Lecture, 1881. Both in the posi- 

 tions of Thomson and Tait and of 

 Helmholtz the principle of energy 

 is, however, like Lavoisier's prin- 

 ciple, purely a regulative, not a 

 constructive, principle of scientific 

 research. It exerts a control and 

 enables us to check the correctness 

 of results. Both in chemistry and 

 physics other principles or methods 

 are required for extending — not 

 merely correcting — our knowledge. 

 Such principles are in the abstract 

 sciences the formula of gravitation, 

 the atomic theory, the ether ; in the 

 natural sciences the morphological 

 and genetic theories. The whole 

 domain of physics and chemistry 

 has been reviewed for teaching pur- 

 poses from this point of view by 

 Hans Januschke, ' Das Princip der 

 Erhaltung der Energie,'' Leipzig, 

 1897. See p. 14 sqq. 



^ Although the history of thought 

 has more to do with theories than 

 with the mere discovery of facts, 

 and with the latter mainly when, 

 as in exceptional instances, they 

 change the scientific aspect of phe- 

 nomena, I think it important to 

 mention specially the great merit 



of Victor Reguault's experimental 

 researches. How much the progress 

 of phj'sical and chemical theory is 

 indebted to his elaborate and ex- 

 tremely accurate measurements of 

 many physical constants may be 

 seen by the perusal of Lord Kel- 

 vin's earlj' memoirs on the dynami- 

 cal theory of heat. The several 

 (so-called) laws of Boyle, Dulong, 

 and others were subjected by Reg- 

 uault to exhaustive tests ; the be- 

 haviour of steam in the steam- 

 engine formed a subject of 

 elaborate investigation ; the proof 

 that chlorine could be substituted 

 for hydrogen in hydrocarbons sup- 

 plied a prominent support to the 

 chemical theories of Laurent. In 

 general Regnault's work is a model 

 of accuracy supported by great in- 

 genuity in the construction of 

 apparatus and the surmounting 

 of difficulties. Like Liebig, he was 

 the master of many pupils who sub- 

 sequently became eminent. Besides 

 being professor of chemistry and 

 physics in Paris, Regnault was 

 actively connected with the cele- 

 brated porcelain works of Sevres. 

 Similar remarks might be made 

 with reference to the labours of 

 Hermann Kopj), who v?as for many 

 years probably the only professor 

 of physical chemistry in Germany. 



