PROCEEDINGS. 



Mendelejeff attacked the question more courageously. The former was 

 probably the first in the field, but the latter must be considered the true 

 parent of the system, for while the former made up a table and pointed 

 out many resemblances between the elements, some of which indeed 

 escaped Mendelejeff, the latter not only proposed a table of the elements, 

 but boldly altered the atomic weights of certain of the elements when 

 they did not conform to his table, and did not merely lay them one side 

 to await what the future might decide concerning them. He did more 

 than this, he said in effect " My classification is correct but there are 

 many spaces where elements are wanting; this does not effect the table 

 it simply means that some elements are as yet undiscovered. I shall 

 describe three of these," said he, "and without claiming to be a prophet, 

 will indicate wheie they are likely to be found." He named them pro- 

 visionally Ek a- "boron, Eka-silicon and Eka-cadmiurn. Within a few 

 years two of these were discovered and their properties agreed almost 

 identically with those which he had suggested. He altered the atomic 

 weight of Ce. from 92 to 140, U. from 120 to 240, and made other 

 changes. His prophecies were unnoticed or jeered at ; his suggested 

 changes were ridiculed. He fought his cause single-handed but his 

 triumph was complete, and came quickly. In less than ten years from 

 his announcement of the Law, the specific heat of Ce. was redeterrnined 

 by means admitting of very slight error, and 'the atomic weight was 

 proved to be 140 or nearly so, much nearer 140 than 92. Uranium was 

 by the same means soon proved to have the proposed weight, viz, 240. 

 Chemists then began to examine his predictions more respectfully and 

 were soon surprised (if chemists are ever guilty of surprise) when in 

 1879-SO Nilson, followed by Cleve, proved the existence of Eka-boron 

 under the name of Scandium; and when in 1886 Winkler proved Eka- 

 silicon to exist as Germanium, Mendelejeff's triumph was complete. Few 

 now doubt the truth of the law, and it has become a powerlul weapon 

 in the hands of the investigator. The line of the classification is com- 

 plete, the actual basis is probably not known as yet, it may be the atomic 

 weights, as is most usually assumed; it may be a common element as is 

 being quietly proposed, though as yet unsupported by experimental 

 evidence; it may be some property as yet unsuspected but that the order 

 is nearly or quite correct no one doubts. 



But where comes in the importance of the rare earths? A glance at 

 either form of table will show blanks. No one doubts that these will 



