IX 



gestion. These were followed by congestion of tlie lungs, of which he died 

 on the 15th of March 1863. 



EiLHARDT MiTSCHERLiCH WES bom on the 7th of January 1794, in 

 the village of Jever in Oldenburg. His father was pastor of Neuende; his 

 uncle, the well-known philologer, was Professor in Gottingen. He was 

 educated at the Gymnasium of Jever, under the historian Schlosser. 

 Following the example of his uncle, and encouraged by Schlosser, he 

 devoted himself to the study of history, philology, and especially the 

 Persian language. In order to prosecute these studies, he went in 1811 

 to the University of Heidelberg, and in 1813 to Paris. He had hoped to 

 be allowed to accompany an embassy to Persia, but was prevented by the 

 fall of Napoleon. In 1814, on his return to Germany, he commenced 

 writing a history of the Ghurides and Kara-Chitayens, compiled from 

 manuscripts in the Gottingen Library, and of Vv^hich a specimen was 

 published in 1815 under the title " Mirchondi historia Thaheridarum." 

 Unwilling to renounce his favourite project of travelling in Persia, he de- 

 termined to accomplish it without any extraneous assistance. The only 

 way in which it appeared possible to travel was in the character of a phy- 

 sician; accordingly he resolved to study medicine. He went to Gottingen 

 for this purpose, and first applied himself to the introductory sciences, 

 especially to chemistry, which so fascinated him that he gave up philo- 

 logy and his intention to visit Persia. In 1818 he went to Berlin for the 

 purpose of obtaining license to lecture. Link allowed him to carry on his 

 researches in the laboratory of the University. Here he undertook the 

 examination of the phosphates and arseniates, and confirmed the accuracy 

 of the latest conclusion arrived at by Berzelius, viz. that phosphoric and 

 arsenic acid contain each five equivalents of oxygen, while phosphorous 

 and arsenious acid contain three equivalents. He noticed at the same 

 time that the similarly constituted phosphates and arseniates crystallized 

 in similar forms. Up to this period he had never paid any especial atten- 

 tion to crystallography, but the conviction that he was on the eve of a 

 great discovery allowed him no rest ; he studied the laws of crystallo- 

 graphy, learned the method of measuring the angles of crystals, and soon 

 satisfied himself that the phosphates and arseniates are not merely similar 

 but identical in form, and that, consequently, bodies exist of dissimilar 

 composition having the same crystalline form, and that these bodies are 

 compounds containing respectively the same number of equivalents. Many 

 minerals appeared to confirm this law, viz. the carbonates, dolomite, chaly- 

 bite, diallogite and calcite, and the sulphates, baryte, celestine, and Angle- 

 site. In confirmation, however, of this discovery he considered it neces- 

 sary to appeal to artificial salts which crystallize readily and distinctly, and 

 are easily obtained of sufficient purity, so that his conclusions might be 

 confirmed by any one without difficulty. The neutral sulphates of prot- 

 oxide of iron, oxide of copper, oxide of zinc, and magnesia, which all con- 



