THE PROGRESS OF SCIENCE 



285 



commerce and labor has been added to 

 the cabinet, it would be only decent to 

 provide for a secretary of education. 

 There is probably no other nation with- 

 out a department of education. The 

 salary of the commissioner of educa- 

 tion is $3,500, and the powers of his 

 office are very limited. The bureau 

 has charge of education in Alaska and 

 prepares an annual report containing 

 statistics and papers on education; but 

 this is all. It may be wise to let the 

 work of the government for education, 

 science and art be distributed among 

 different departments on the financial 

 side. But there should be cooperation 

 and a great extension of what is now 

 being done. The Bureau of Education 

 is the natural center, and Ave may look 

 to a great enlargement of its powers 

 and influence in the near future. 



PROFESSOR MENDELEEFF. 



Dimitri Mendeleeff, the greatest of 

 Russian chemists, was born in Siberia 

 seventy-two years ago. From 1856 till 

 1S59 he was an instructor "at the Uni- 

 versity of St. Petersburg. After two 

 years of study at Heidelberg, he re- 

 turned to Russia in 1861. Two years 

 later he was made professor of chem- 

 istry at the Technological Institute in 

 St. Petersburg and was transferred to 

 the university in 1866. 



From the beginning Mendeleeff has 

 been interested in theoretical problems. 

 His first paper was on isomorphism. 

 For years he worked on the relations 

 between specific volumes and other 

 properties. While others, notably 

 Kopp, have worked along similar lines 

 without making any great generaliza- 

 tion in consequence, it must be ad- 

 mitted that Mendeleeff's great dis- 

 covery of the periodic law seems a 

 natural development from the earlier 

 work. 



In 1869 Mendeleeff announced that if 

 the elements be arranged in the order 

 cf their atomic weights, it will be 

 found that similar variations in their 

 chemical properties repeat themselves 



periodically, and that the order of the 

 faculty of the elements to combine with 

 other elements also corresponds with 

 the order of their atomic weights. 



Like many another important gen- 

 eralization, the real significance of this 

 one is not self-evident. Before the 

 periodic law was formulated, the 

 atomic weights of the elements were 

 purely empirical numbers, and it was 

 not always easy to tell what multiple 

 of a given value should be taken as 

 the true atomic weight. This was 

 changed by Mendeleeff's discovery. The 

 periodic law made it possible to de- 

 termine the atomic weights of yttrium, 

 indium and beryllium, for instance. 

 Mendeleeff went further than this. He 

 pointed out that there were gaps in the 

 table; that these must correspond to 

 unknown elements; and that the prop- 

 erties of these unknown elements could 

 be predicted from those of the known 

 elements surrounding the gaps in the 

 table. C allium, scandium and german- 

 ium have since been discovered and have 

 the properties assigned to them in ad- 

 vance by Mendeleeff. 



A more striking, though less dram- 

 atic, proof of the soundness of Men- 

 deleeff's generalization is to be found in 

 the fact that the inert gases of the 

 atmosphere, argon, helium, neon, etc., 

 find places in the classification, though 

 the possibility of there being such sub- 

 stances was not suspected in 1869. It 

 is not too much to say that the periodic 

 law of Mendeleeff is recognized to-day 

 as the only basis for the classification 

 of the elements. Only two contradic- 

 tions have been found in nearly forty 

 years. The atomic weights of the ele- 

 ments, iodine and tellurium, should be 

 transposed to make these substances fit 

 into the table, and there is no place for 

 most of the so-called rare elements. 

 The first difficulty will disappear if any 

 one can show that either tellurium or 

 iodine contains an unknown impurity. 

 It must be admitted that the chances 

 of this are not good at present. 



We can avoid the difficulty as to the 

 rare earths by considering a group erf 



