THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 81 



the number and weight of all chemical elementary principles 

 which enter into any sort of combination one with another."* 



From these most interesting notes it appears that the origin 

 of Dal ton's Atomic Theory was not an attempt to explain the 

 fact that combination may occur between the same two sub- 

 stances in more than one proportion,! but an attempt to render 

 intelligible a group of physical phenomena. In the course of 

 this attempt, Dalton turned for data of the relative weights of 

 his atoms to the determination of the composition of different 

 substances that had been made by contemporaries of repute : 

 being already, from his physical considerations, convinced that 

 chemical combination takes place between particles of different 

 weights. " The extension of this idea to substances in general 

 necessarily led him to the law of combination in multiple pro- 

 portions," J and thus, as the result of this renewed application 

 of the concept of the atom, a new definite problem was 

 presented to chemists which has guided their researches ever 

 since ; a problem which would generally be stated as that of 

 determining what atoms of the elements enter into the com- 

 position of the " compound atom " or molecule of every 

 compound. 



31. 



In the face of these historical facts it seems somewhat 

 paradoxical to maintain, as Professor Divers does in his 

 Presidential Address to the Chemical Section of the British 

 Association, that the atomic theory propounded by Dalton 

 " is not founded upon the metaphysical conception of material 

 discontinuity, and is not explained or illuminated by it."|| 



* Roscoe and Harden, op. cit., p. 17. 



t This common belief is due to Thomson, History of Chemistry, i, p. 80, 

 ii, p. 291. 



J Koscoe and Harden, op. cit., p. 51. 



B.A. Reports, 1902, pp. 557-75. Cf. the criticism of Divers' views 

 by Meldrum, Avogadro and Dalton, 1904. 



|| P. 558. 



G 



