OP ARTS AND SCIENCES. 165 



Lothar Meyer on the same general subject says, " There can be no 

 doubt as to the fact that these differences are subject to law";* and, 

 " There is still much work for the hands and mind ; but it will be 

 thoroughly rewarded. The prize is a systematic inorganic chemistry 

 which will bear comparison witli the thoroughly developed system 

 of organic chemistry." j 



The object of this paper is to contribute to the removal of these 

 difficulties, by showing that the increase in the atomic weights of the 

 elements follows a law of the utmost simplicity in its general form, 

 and identical with that of the series of organic compounds. 



Let us take the series above mentioned and consider whether any of 

 its terms can be classed in a series of constant increase. Beginning 

 with 2 as a modulus, we find that it applies to 7, 9, and 11, with no 

 recurrence of this difference except for the terms 12, 14, 16 ; 3 applies 

 only to 9, 12,-24, 27,-48, 51, and to 16, iQ * * 28, 31 * * * * * 52, 

 55; 4 however applies to 7, 11 * 19, 23, 27, 31, 35, 39 * * 51, 55. 

 59, and to 12, 16 * 24, 28, 32 * 40, 44, 48, 52, 56; thus embracing 

 in two parallel series all the terms of the first three periods of New- 

 lands and Mendeleeff, with the exception of 9 and 14, i. e. 22 out of 

 24. The probability that these numbers would so far coincide with 

 the regular series from the i-esult of chance, is too slight to be enter- 

 tained. If now, in addition to this coincidence, any points of resem- 

 blance can be discovered among several of the elements in each series, 

 such resemblances are significant; but when it appears that all or 

 nearly all in each series fall into a distinct group that has already been 

 recognized as such by chemists, there is scarcely room for doubt that 

 the regularity of the series is connected with the intrinsic nature of 

 the elements. 



Those of the first series are all Perissads and those of the secoi.d 

 Artiads, or elements of uneven and even quantivalence respectively, 

 with the single exception in one case of scandium, a newly discovered 

 element whose atomic weight has never been so accurately determined 

 as to throw it out of its group, and cobalt and nickel, which apparently 

 belong to another group. For the present, therefore, the law of regu- 

 lar increase in the atomic weight of the parallel series is spoken of as 

 the Law of Artiad and Perissad Increase, or more briefly as the 

 Pkrissad Law. 



By similar methods, we find that the numbers between 70 and 100 



* Modern Theories of Chemistry, English Translation, 1888, p. IGO. 



* Ibid., p. 170. 



