1884.] Remarks on the Atomic Weight of Beryllium. 463 



of the value 9 or 9*2. I did not consider that these remarks called 

 for notice at the time, as they were beside the question immediately 

 under discussion, namely, the experimental determination of the 

 atomic heat of the metal, but from the fact that they have been 

 abstracted for various journals, and that greater prominence has 

 been given to them than was perhaps originally intended by the 

 author, I beg to be allowed to comment upon them, as my opinions 

 have been entirely misrepresented. Dr. Humpidge states in allusion 

 to me : " This chemist concludes from his experiments that glucinum 

 is a dyad metal, and that its homologues are calcium, strontium, and 

 barium, elements with which it has not the slightest analogy." From 

 this sentence it appears probable that Dr. Humpidge was not fully 

 acquainted with the nature of the evidence advanced, which, how- 

 ever, might be excusable, since though the two papers in which it 

 was contained were read at the meetings of the Chemical Society, 

 that " On Homologous Spectra " on March 15th, and that " On the 

 Spectrum of Beryllium " on April 19th, they were not published in 

 the Journal in time for him to have consulted them.* 



The statement quoted above is precisely my argument. " The spec- 

 trum of beryllium exhibits no marked analogy with the calcium, the 

 magnesium, or the aluminium spectra, all of which are members of 

 well-defined homologous series." 



" There is nothing similar to the boron, the silicon, or carbon spec- 

 trum, nor to those of scandium, yttrium, or cerium. The spectrum of 

 lithium is the one most allied to that of beryllium in the number, the 

 relative positions, and intensity of the lines. The question, however, 

 whether beryllium is a dyad, and the first member of the series mag- 

 nesium, zinc, cadmium, is complicated, since it would probably present 

 a spectrum of a cTifferent character to the succeeding homologues, in 

 accordance with the following equation, which follows from the 

 periodic law and holds good for the chemical properties of com- 

 pounds :" — 



Li : Mg=Be : A1=B : Si. 



" The relation of the spectrum of lithium to that of magnesium is 

 obscure, that of boron to silicon less so, consequently we might expect 

 that the relation of the beryllium spectrum to that of aluminium 

 would not be well defined." 



It is further remarked by Dr. Humpidge : " And it seems strange 

 that Professor Hartley should consider some slight spectroscopic 

 resemblance between glucinum and the metals of the alkaline earths 



* The latter paper, which appeared first, was published in the June number of 

 the " Journal of the Chemical Society," which reached me through the post on 

 June 7th, its date of issue was therefore scarcely likely to be earlier than the 5th. 

 The paper " On Homologous Spectra" was delayed until September. 



