364 [Proc. B.N.F.C., 



by Mendelejeff (1869), which is now generally known as 

 " Mendelejejf s Periodic Law.' 1 



Hydrogen being the lightest element in atomic weight of 

 all our known terrestrial elements is adopted as the unit 

 and standard from which the other elements take their 

 relative weight ; and the elements gradually increase in atomic 

 weight as the notes of the music scale ascending increase in the 

 number of vibrations t>er second by which they are produced. 

 Hydrogen being the lightest, the other elements are counted 

 as so many Hydrogens in weight. The first seven substances 

 going up in the order of their increasing atomic weights shew 

 certain physical and chemical characters, just as the seven notes 

 of the musical octave have certain tonal characters by which 

 they can at once be detected and named in any musical com- 

 position. After Hydrogen which is the unit and standard, 

 Lithium is 7 Hydrogens in weight; Beryllium is 9 ; Boron 11; 

 Carbon 12 ; Nitrogen 14 ; Oxygen 16 ; and Fluorine 19. This 

 is the first octave. In the second octave we have Sodium 23, 

 corresponding to Lithium ; Magnesium 24, corresponding to 

 Beryllium ; Aluminium 27, to Boron ; Silicon 28, to Carbon ; 

 Phosphorus 31, to Nitrogen ; Sulphur 32, to Oxygen ; and 

 Chlorine 3^5 to Fluorine. These are the first two octaves of 

 the chemical elements. After these, which are called the 

 typical pair, there comes an interesting and somewhat 

 mysterious pair of octaves with three " transitional elements " 

 between them. These transitional elements also occur between 

 the third pair ; and the same thing recurs between the fourth 

 and fifth pairs ; and it may be that three may be found between 

 the two octaves of the sixth pair ; or it may turn out that this 

 last pair may be like the first, a typical pair, without the 

 so-called transitional elements. Thalium which is 232 Hydrogens 

 in atomic weight, and Uranium which is 239*8 are the heaviest 

 substances yet discovered ; they belong to the eleventh octave. 

 The whole of the twelfth octave is yet awanting. But inas- 

 much as the octaves of the chemical elements are linked 

 together by these transitional triads in pairs ; and inasmuch as 



