TRANSACTIONS OF SECTION B. 597 



differences between masses of tangible size. It became conceivable that matter 

 in the state of gas or vapour might become so attenuated that repulsion of the 

 molecules would be greater than' the attraction ; that they would then no longer 

 form aggregates, and in consequence would cease to be weighable. _ In such a 

 condition they may be imagined to constitute the ether, and in view of this 

 conception there may be recognised four physical conditions of material substances, 

 namely, solid, liquid, gas, and ether. 



It is more than twenty years ago since the study of homology in spectra led 

 me to the conviction that "the chemical atoms are not the ultimate particles of 

 matter, and that they have a complex constitution. 



That the atoms of definite groups of chemically related elements are composed 

 of the same kind of matter in different states of condensation is not a dream or a 

 view of a visionary character, for it is based upon definite observations controlled 

 by exact physical measurements, and is therefore in the nature of a theory rather 

 than an hjrpothesis. Batchinski (1903) regards the atoms as being in a state of 

 vibration, and the periods of vibration of related elements appear to stand in a 

 simple relation to their properties. The mass of an atom is proportional to the 

 square of its period of vibration, and conversely the vibration period of the atom 

 may he calculated from the square root of the atomic weight. These values have 

 been calculated and arranged according to Mendeleef's classification, whereby it is 

 shown that there is a decided tendency to form harmonic series in the vertical 

 columns. The deviations are probably capable of explanation, as the author 

 believes, on the ground that the atom is not to be regarded as a material point, 

 but as a material system. It is well to remember that the precursor of the 

 Periodic Law was Newland's Law of Octaves. 



I have always experienced great difficulty in accepting the view that because 

 the spectrum of an element contained a line or lines in it which were coincident 

 with a line or lines in another element it was evidence of the dissociation of the 

 elements into simpler forms of matter. In my opinion, evidence of the compound 

 nature of the elements has never been obtained from the coincidence of a line or 

 lines exclusively belonging to the spectrum of one ele^ment with a line or lines in 

 the spectrum exclusively belonging to another element. This view is based upon 

 the following grounds :— First, because the coincidences have generally been shown 

 to be only apparent, and have never been proved to be real ; secondly, because the 

 great difficulty of obtaining one kind of matter enth'ely free from every other kind 

 of matter is so great tliat where coincident lines occur in the spectra of what have 

 been believed to be elementary substances they have been shown from time to time 

 to be caused by traces of foreign matter, such as by chemists are commonly termed 

 impurities ; thirdly, no instance has ever been recorded of any homologous group of 

 lines belonging to one element occurring in the spectrum of another, except and 

 alone where the one has been shown to constitute an impurity in the other ; as, for 

 instance, where the triplet of zinc is found in cadmium and the triplet of cadmium 

 in zinc ; the three strongest lines in the quintuple group of magnesium in graphite, 

 and so on. The latest elucidation of the cause of coincidences of this kind arises 

 out of a tabulated record from the wave-length measurements of about three 

 thousand lines in the spectra of sixteen elements made by Adeney and myself. 

 The instances where lines appeared to coincide were extremely rare ; but there was 

 one remarkable case of a group of lines in the spectrum of copper which appeared 

 to be common to tellurium ; also lines in indium, tin, antimony, and bismuth which 

 seemed to have an origin in common with those of tellurium. 



It is difficult to separate tellurium from copper, and copper from tellurium, by 

 ordinary chemical processes. Dr. Kothner, of Charlottenburg, has succeeded in 

 obtaining A'ery pure tellurium from the spectrum of which these lines and also 

 several others have been almost entirely eliminated, which shows that they are 

 foreign to the element, and that his specimen of tellurium is probably purer than 

 any previously obtained. For determining the atomic weight of telluriimi it is of 

 course necessary to obtain it in the greatest possible state of purity ; and it may 

 be mentioned that the material which Staudenmaier employed for this purpose 

 was found, from Kiithner's photograph of its spectrum, to be a very pure specimeu. 



