388 M. C. Lea — Atomic 'Weights of the Elements. 



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last group of elements having nothing 

 in common with other elements cannot be 

 classed with them and will probably be found, 

 when we know much more than we do now, 

 to have a wholly different constitution. 



There are several things worthy of remark 

 in the above table. It will be seen that the 

 differences at first approximate to 16. Then 

 comes a long set of differences, twenty in 

 number, beginning with 41*3 and gradually 

 but not regularly increasing to 49. The 

 remaining differences are all exactly 88 with 

 one exception of 90, but as this is the dif- 

 ference between two metals of which com- 

 paratively little is known and whose atomic 

 weights cannot be considered as being accu- 

 rately fixed (indium and thallium), it is quite 

 probable that this exception may hereafter 

 disappear. 



It should be remarked that when the set 

 of differences approximating 16 is once left 

 behind, this difference does not reappear in a 

 single case. The same is true of the differ- 

 ences averaging 45 : this class of differences 

 does not once reappear when 88 is reached. 



For some time past it has been believed 

 that the oxygen group does not end with 

 tellurium but contains still another member 

 with a higher atomic weight. It will be 

 observed that in both the above tables there 

 remains a space for such an element. Its 

 atomic weight should exceed that of tellu- 

 rium by the difference 88 and should there- 

 fore be 213. Finally it may be said that the 

 blanks in the table of differences are due to 

 corresponding blanks in the table of atomic 

 weights. 



The change just mentioned in the classifi- 

 cation of cerium and of gold makes a slight 

 change in the table representing the whole 

 range of elements in series. I therefore 

 reproduce this table as corrected. 



It will be observed that all the elements 

 having only colorless ions appear on the 

 base line. The elements having ions always 

 colored appear on the upper line parallel 

 to the base line. The transition elements 

 appear on the inclined lines. 



