1896-97.] 3^5 



two of the elements of the eleventh octave have been discovered; 

 Mendelejeff confidently anticipates the twelfth octave of elements; 

 for which the eleventh has, so to speak, lifted up its voice and 

 cried for its undiscovered mate; while of itself, also, only 

 Thalium and Uranium, the fourth and sixth, have as yet been 

 discovered. When the Periodic Law was first promulgated by 

 Mendelejeff (1869) there were a number of instances in which 

 the system did not harmonise with the then accepted atomic 

 weights of the elements. Mendelejeff boldly asserted that the 

 atomic weights, and not the Periodic System, were at fault ; 

 and in every such case the careful reinvestigation of the atomic 

 weights by numerous chemists has proved the correctness of his 

 assertion. In the case of Indium e.g. it had been counted 76 

 Hydrogens. It did not suit that place in the system, and when 

 corrected later on it was found to be 113 Hydrogens, and 

 found its place in the sixth octave, as the third of that octave. 

 Again Beryllium, at first called Glucinum, was counted IJ'8 

 Hydrogens, but there was no place for it between Carbon 12 

 and Nitrogen 14, in the first octave. According to its properties 

 it was needed between Lithium 7 and Boron II. When 

 corrected its atomic weight was found to be Q Hydrogens, and 

 so its place was between Lithium and Boron. These were 

 excellent confirmations of the Periodic Law as an ordinance of 

 Nature. 



And not only has the Periodic Law been of service in 

 bringing about the correction of numbers of doubtful atomic 

 weights ; but by means of it Mendelejeff predicted the existence 

 of undiscovered elements, and even described their properties. 

 There were gaps in the third and fourth octaves awaiting 

 elements. In 1875 Gallium was discovered, and exactly fitted 

 the place with atomic weight 70 after Zinc 65 in the fourth 

 octave. And in 1886 Germanium was found, with atomic 

 weight 72, which was needed between Gallium Jo and Arsenic 

 J5, with the very properties for the place. And Scandium 44 

 which was needed as third in the third octave between Calcium 

 40 and Titanium 48, was discovered in 1879, with weight and 



