72 Mr. Henry Wilde on the 



directly with the hydrogen unit alone by Stas and the 

 older chemists. 



It will be observed that there are gaps in the positive 

 series H«, to be occupied by two elements, with atomic 

 weights 154 and 177, and by their homologues of position 

 in the series H2/2, with atomic weights 160 and 184, which 

 remain to be discovered. It will be evident that the 

 specific gravities and other properties of these elements can 

 be predicted with the same certainty as the atomic weights. 

 The multiple relations subsisting among the series 

 H3?z are highly interesting on account of the recent 

 additions that have been made in it by the aid of spectral 

 analysis, and the questions raised respecting the classification 

 and quantivalence of some of its members, which, from 

 their rarity, have not been sufficiently investigated. The 

 atomic weights of this series are calculated on the same 

 principle as those shown in the series H/z, H2n, and are 

 multiples of H3. 



H 3 « 



o . o . 12 = C = 12 



1x27- o = Al= 27 



2 x 27 — 12 = Sc = 42 



3x27 — i2 = Ce= 69 



4x27 — i2 = Ga= 96 



5x27-12 =Y = 123 



6 x 27 - 12 = In = 150 



7 x 27 - i2 = E = 177 

 8x27 — 12 = Tl =204 

 9 x 27 — 12 = Th =231 



It will be seen that where the numbers in the table differ 

 from the experimental determinations, the differences are 

 either multiples or submultiples of the received atomic 

 weights ; and, as the theoretic atomic weights of Th, Tl, 

 Al, and C are identical with the actual determinations, and 

 that triads are formed by Tl, In, Ga, Sc, and Th, E, Y, Ce, 

 as in the series Hn, H2«, there is a high degree of proba- 



