482 Journal of Applied Microscopy. 



The precious stones ruby, sapphire, topaz, emerald, cats-eye are, in trans- 

 parency, between diamond and quartz. Turquois differs materially from its 

 imitations, true pearls are more transparent than artificial, and in general the 

 true stones differ notably in transparency from their imitations. 



II. The Development of Fluorescence and Phosphorescence by the Roentgen 

 Rays. — The X-rays produce luminescence in certain amorphous substances, such 

 as uranium glass, and in crystals of certain salts and minerals. Fluorite becomes 

 so strongly luminescent, that if added in fine powder to the photographic plate, 

 the time of exposure for X-ray photographs may be shortened. Celestite, barite 

 and strontianite produce similar effects. Diamond, apatite, autunite and scheelite 

 become strongly luminescent, and many lead compounds feebly so. 



III. Refraction of Roentgen Rays. — Prisms of water, carbon disulphide, and 

 aluminum produce no refraction ; with iron prisms there was very slight refrac- 

 tion, the index of refraction differing from unity not more than 0.0005. With 

 a diamond prism the index of refraction differed from unity less than 0.0002, 

 evidently within the limits of error in observation. 



IV. Polarization and Dichroism of the Roentgen Rays. — The X-rays would 

 be polarized if in different directions there is unusual absorption. No such 

 difference was found in quartz, epidote or apatite, and in other minerals the 

 results were negative. 



V. Uranium and Thorium Rays. — Zinc sulphide and calcium sulphide pro- 

 duce an image on a photographic plate wrapped in black paper, that is, evolve 

 rays which penetrate the paper. Uranium salts especially show the property. 

 The rays from such substances penetrate most material even more easily than 

 the X-rays. a. j. m. 



„ • , f T- . „ XT This paper is a record of probably the 



Morozewicz, Jozef. Expenmentelle Unter- \ ^ . ^ . -^ 



suchungen iiber die Bildung der Minerale most important work in mineral syn- 



lT•..^^^«"'^• Tschermak's Min. u Petr. thesis since the researches of Fouque 

 Mitt. 18: 1-94, 105-240, 1898. . ^ . ^ 



and Michel-Levy*. The experiments 



extended practically without interruption through over five years, and differ from 

 those of Fouque and M-Le'vy in that, instead of using small (20 cm. diam.) plati- 

 num crucibles in a laboratory furnace, large crucibles were inserted in one of 

 the open-hearth furnaces of the glass works at Warschau. In this way much 

 larger crystals were obtained, which could be separated and chemically analyzed, 

 instead of relying solely upon examination with the microscope. 



The furnace was in use throughout as a glass furnace, two openings (canals) 

 were made in the walls one and one-half feet long, through which the crucibles 

 could be inserted and withdrawn, and these were closed by suitable slabs. For 

 melting, large crucibles were used, but after melting it was found most satis- 

 factory to devitrify and crystallize in Chamotte crucibles of 150 cc. capacity. 



The mixtures were prepared to correspond to analyses of unaltered, well 

 crystallized, and typical eruptive rocks. For instance : for granite the mixture 

 corresponded to the liparite of Iceland, for syenite to the trachyte of Ischia, 

 and for basalt to the dolerite of Londorf. The bases were added as carbonates, 

 hydrates or oxides, the silica as SiOa- 3 H2O. 

 *Synthese des Mineraux et des Roches. Paris, 1882. 



