228 Alexander Petrunkevitch, Ph.D., 



predict the existence of the yet unknown, missing elements as 

 well as their atomic weight and properties. This prediction is 

 justly likened to the prediction of the planet Neptune by Leverrier 

 from his mathematical calculations. And indeed two years after 

 the prediction in 1871, the first element was discovered, and 

 called gallium (Alendelejetif proposed the name ekaboron). In 

 1879 was discovered scandium (Mendelejefif's ekaaluminium ) and 

 in 1886 germanium ( Mendelejeff's ekasilicon). In several cases 

 MendelejelT ventured to question the correctness of the commonly 

 accepted atomic weights, because they did not fit rightly into his 

 periodic system and later investigations proved the correctness 

 of his assertion. In 1888 he made an exhaustive study of the 

 Donetz anthracite industry and was subsequently appointed 

 member of the council of trade and manufacture. To this period 

 belongs also his work on smokeless powder done at the request 

 of the ministry of war. In 1893 he resigned his professorship to 

 become Director of the Bureau of Weights and Measures. In 

 1902 in a paper on the chemical conception of ether he gave 

 expression to a hypothesis that ether is a gaseous element with 

 an atomic weight smaller than that of hydrogen. Mendelejefif 

 died in 1907 and the list of his works comprises over 140 titles 

 including many investigations in various branches of physical 

 chemistry, such as indefinite solutions, expansion of liquids with 

 heat, etc. 



But for lack of space it would be unjust to pass in silence over 

 the splendid work done by Russian chemists in recent years. I 

 cannot refrain however from mentioning V. N. Ipatiev's exten- 

 sive researches in organic chemistry, especially in hydrogenation 

 of oils ; and I. I. Ostromuislenskii's investigations of rubber. 



In the closely interrelated sciences of crystallography, miner- 

 alogy, petrography, and physical geology, several names stand 

 out amidst a number of less known investigators. Ewgraf Step- 

 anovitch Fedoroff was the first to prove that all crystals belong 

 to the one or the other of the 32 possible types of symmetry and 

 created the nomenclature afterwards accepted by Grote and 

 others. He was a productive worker and made many researches 

 in geometry, crystallography, geology, physical and descriptive, 

 ores, etc. 



His pupil and my teacher in crystallography and mineralogy, 

 Wladimir Ivanovitch Vernadsky, one of the broadest and best 



