Page:Popular Science Monthly Volume 69.djvu/289

Rh 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 without a department of education. The salary of the commissioner of education 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 we may look to a great enlargement of its powers and influence in the near future.

the greatest of Russian chemists, was born in Siberia seventy-two years ago. From 1856 till 1859 he was an instructor "at the University of St. Petersburg. After two years of study at Heidelberg, he returned to Russia in 1861. Two years later he was made professor of chemistry at the Technological Institute in St. Petersburg and was transferred to the university in 1866.

From the beginning Mendeléeff 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 generalization in consequence, it must be admitted that Mendeléeff's great discovery of the periodic law seems a natural development from the earlier work.

In 1869 Mendeléeff 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 generalization, 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 Mendeléeff's discovery. The periodic law made it possible to determine the atomic weights of yttrium, indium and beryllium, for instance. Mendeléeff went further than this. He pointed out that there were gaps in the table; that these must correspond to unknown elements; and that the properties of these unknown elements could be predicted from those of the known elements surrounding the gaps in the table. C allium, scandium and germanium have since been discovered and have the properties assigned to them in advance by Mendeléeff.

A more striking, though less dramatic, proof of the soundness of Mendeléeff'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 substances was not suspected in 1869. It is not too much to say that the periodic law of Mendeléeff is recognized to-day as the only basis for the classification of the elements. Only two contradictions have been found in nearly forty years. The atomic weights of the elements, 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 of