428 Intelligence and Miscellaneous Articles. 



The experiments were made from the middle of May to the 

 middle of June in this year (1889). — Wiedemann's Annalen^ 

 vol. xxxviii. p. 40 (1889). 



AND MANGA- 

 NESE IN THE SULPHIDES OF THE ALKALINE EARTHS. BY V. 

 JgLATT AND PHILIPP LENARD. 



The results of a long series of researches on the phosphorescence 

 of the alkaline earths are summed up by the authors as follows : — 



(1) The strongly luminous lime-phosphorescent s are mixtures of 

 three essential constituents ; sulphide of calcium, the active metal, 

 and a third body which, when present alone in calcium sulphide, is 

 not active. It is very probable that perfectly pure calcium sulphide 

 does not phosphoresce. 



(2) The bands which occur in the spectra of the lime-phospho- 

 rescents show that the active metals are manganese, copper, 

 bismuth, and a fourth metal which is not known. To each of 

 these metals a band corresponds which is invariable in position. 



Extremely small quantities of the metal are active. The inten- 

 sity of the phosphorescence at first increases with its quantity, and 

 then decreases to zero. The quantities which exhibit the maximum 

 action are very small. 



(3) The additions used by us as the third constituent are colour- 

 less salts, and all of them fusible at the temperatures at which the 

 phosphorescents are prepared. Hence they coat the surface of the 

 calcium sulphide causing the mass to sinter together, and the active 

 metal produces a delicate tint which is essential for the phos- 

 phorescence. — Wiedemann's Anncden, vol. xxxviii, p. 90 (1889). 



ON STEATITE AS A SOURCE OF ELECTRICITY* 

 BY M. MENTZNER. 



Steatite, when rubbed with gun-cotton, or with Kienmayer's 

 amalgam, or with fur, becomes negatively electrified, and in the 

 electrical series is on the extreme left. For these experiments 

 a prism with rounded edges, 8 centim. in length, 3*5 centim. in 

 breadth, and 3 centim. in thickness is used, in which there is a 

 hole for an ebonite rod. In the upper surface a semicylindrical 

 groove is cut by means of a glass rod and emery-paper. If a glass 

 or ebonite rod is drawn through it, it becomes positively and the 

 steatite negatively electrical. 



A kind of electrical machine may be made from a cylindrical 

 rod of steatite fixed to a handle of ebonite ; a loop of copper wire 

 is fastened round it, the ends of which are twisted together and 

 terminate in a knob, which is held over a flat metal vessel full 

 of bisulphide of carbon. When the steatite is struck with a fox's 

 brush the bisulphide is ignited by the spark produced. — Zeitschrift 

 fiir phys. unci chem. Unterricht. ii. pp. 241-243 (1889) ; Beibldtter 

 'der Physik, vol. xxii. p. 707 (1889). 



