LECTURE XV.] HISTORY OF CHEMISTRY. 319 



and of Glan. 123 Finally, there are the numerous researches 

 which are directed towards establishing relations between the 

 emission spectra of the elements, such as those of Lecoq de 

 Boisbaudran 124 and of Ciamician ; 125 or between the absorption 

 spectra of compounds, such as those of Abney and Festing, 126 

 of Kriiss, 127 and others. 



Forming a counterpart to this analytical method there is 

 also a synthetical one, to which, however, the same general 

 applicability that the former possesses cannot be attributed. I 

 refer to the synthesis of minerals. A stimulus to making ex- 

 periments of this kind was supplied by observations made by 

 Koch (iSoQ), 128 and especially by Hausmann and Mitscher- 

 lich, who found, amongst the slags obtained in metallurgical 

 processes, products which proved to be identical with known 

 minerals. The first successful experiment of this kind originated 

 with Sir James Hall, who prepared crystallised carbonate of lime 

 (marble) by heating the carbonate under pressure. 129 Berthier 

 and Mitscherlich obtained artificial mica, pyroxene, and similar 

 minerals by fusing silica with lime, magnesia, and ferric 

 oxide. 130 Gaudin prepared small rubies by fusing alumina 

 (obtained by heating ammonia alum) in the oxyhydrogen blow- 

 pipe, after the addition of some chromic oxide. 131 Gay-Lussac 

 obtained crystallised haematite by the action of water vapour on 

 ferric chloride. 132 Ebelmen succeeded in preparing an exten- 

 sive series of difficultly fusible or infusible crystalline minerals 

 by employing borax or boracic acid as a material from which to 

 crystallise them. 133 Becquerel obtained, in the crystalline state, 

 substances insoluble in water, such as silver chloride, silver 

 sulphide, cuprous oxide, basic cupric carbonate, etc., by making 

 use of slowly progressing chemical reactions. 134 



12:5 'Wiedem. Ann. I, 351 ; compare also Hiifner, J. pr. Chem. [2] 

 16, 290. 124 Comptes Rendus. 69, 445, 606, 657, etc. 125 Ber. Wien. Akad. 

 76 (2), 499 ; 79 (2), 8 ; 82 (2), 425. 126 Journ. Chem. Soc. 42, 130-131. 

 127 Berichte. 16, 2051 ; 18, 1426. 128 Ueber krystall. Hiittenproducte. 

 129 Trans. Roy. Soc. Edin. 6, 71 ; compare Gehlen's Journal fur die 

 Chemie, etc. I, 271. 13 Ann. Chim. [2] 24, 355. 131 Annalen. 23, 

 234. 132 Ann. Chim. 80, 163 ; [2] I, 33. 133 Comptes Rendus. 25, 

 66 1 ; Ann. Chim. [3] 22, 21 1. 134 Ann, Chim. [2] 51, 101, 



