Chemistry and Physics. 347 



that the interior of the earth does not contain radium, and that 

 in all probability its composition is quite different in other 

 respects also from that of the surface materials. His data from 

 the quantity of radium in the rocks point to a thickness of at 

 most forty-five miles for the earth's rocky crust. Calculation on 

 these premises, assuming that the conductivity of rock is not much 

 affected by change of temperature, indicates that the bottom of 

 the crust, forty-five miles down, would have a temperature of 

 1500°C. The inside nucleus, heated by this crust of radium- 

 containing material, must be at this uniform temperature 

 throughout. — Chem. News, xciv, 125. ■ h. l. w. 



3. Ionium. — Maeckwald and Keetman state that they have 

 observed that several uranium minerals contain a constituent 

 which is obviously identical with Boltwood's ionium. It follows 

 thorium in the usual chemical processes, and they have been 

 unable to separate it from that element. They explain why a 

 substance of such high emanation power has hitherto escaped 

 discovery by stating that only residues of the Joachimsthal 

 uranium manufacture have been treated on the large scale for 

 the separation of radio-active substances. It appears that these 

 residues are comparatively poor in ionium, as most of this sub- 

 stance probably goes into solution with the uranium during the 

 process. The authors report the surprising circumstance that the 

 mineral autunite, which is a calcium-uranium phosphate occur- 

 ring in beautiful crystals, was found to be free from lead when 

 10 g. of it were investigated. This result, which will be further 

 examined, is of importance because lead is supposed to be the 

 end product of the radio-active transformation of uranium. — 

 JBerichte, xli, 49. h. l. w. 



4. Natural Occurrence of Sodium Fluoride. — Laceoix has found 

 crystallized sodium fluoride as a constituent of an eruptive rock, 

 nephelite-syenite, from the Islands of Los, off the coast of Guinea. 

 The mineral, which has been named villiaumite, occurs in small 

 grains of a carmine color, and the author believes it to be an 

 essential constituent of the rock and not of secondary origin. 

 Being soluble in water it is found only in fresh specimens of the 

 rock. Upon treating a kilo of the rock with boiling water 3 - 5 g. 

 of soluble salts were obtained, consisting chiefly of sodium 

 fluoride, but containing a little sodium chloride, and small quan- 

 tities of other impurities. The mineral is softer than calcite, has 

 a specific gravity of 2 -, 79 and is characterized not only by its 

 color and solubility, but by being isometric in crystallization, 

 and having an index of refraction of l - 328 in sodium light, which 

 is less than that of water or of any other known mineral. — Comptes 

 JRendus, cxlvi, 213. h. l. w. 



5. Mechanical Effect of Temperature on a Gold Leaf Elec- 

 trometer in a Vacuum. — J. Bottomlet describes such an effect. 

 The approach of heated bodies to the exhausted vessel containing 

 the gold leaves caused a movement of these even when the vessel 

 was enclosed in a cage to prevent electrical effects. The leaves 



