Ixxvi 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 where they are likely to be found.” He named them pro- 
visionally Eka-boron, Eka-silicon and Eka-cadmium. 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 prephecies 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 redetermined 
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 powerful 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 
