ol4 Intelligence and Miscellaneous Articles. 



55 volts ; the temperature did not much exceed 2250°. A current 

 furnished by a gas-engine of 8 horse-power was 100 amperes and 

 45 volts produced a temperature of about 2500°. Finally, thanks 

 to the courtesy of M. Violle, we had at our disposal 50 horse- 

 power ; the arc in these conditions measured 450 amperes and 

 70 volts, the temperature was about 3000°. 



With high-tension experiments certain precautions must be 

 taken and the couductors be carefully insulated. Even with 

 currents of 30 amperes and 50 volts, like those used at the 

 beginning of the investigation, the face must not be exposed to a 

 prolonged action of the electrical light, and the eyes must always 

 be protected by means of very dark glasses. Electrical sun-strokes 

 were very frequent at the outset of these researches, and the 

 irritation produced by the arc on the eyes may produce very painful 

 congestion. 



The temperatures given are only approximate ; they will be 

 especially determined by M. Violle by methods to be afterwards 

 described. A certain number of the results obtained are briefly 

 enumerated. 



When the temperature is near 2500°, lime, strontia, and magnesia 

 crystallize in a few minutes. If the temperature reaches 3000° the 

 substance of the furnace itself — quick-lime — melts and runs like 

 water. At this same temperature carbon rapidly reduces calcic 

 oxide, and the metal is liberated freely ; it unites readily with the 

 carbon of the electrodes, forming a calcic carbide, liquid at a red 

 heat, and which can be easily collected. Chromic oxide and magnetic 

 oxide of iron are melted rapidly at a temperature of 2250°. 

 Uranium oxide when heated alone is reduced to protoxide, crystal- 

 lizing in long prisms. Uranium oxide, which cannot be reduced 

 by carbon at the highest temperature of our furnaces, is reduced 

 at once at the temperature of 3000°. In ten minutes it is easy to 

 obtain a regulus of 120 grains of uranium. 



The oxides of nickel, cobalt, manganese, and chromium are 

 reduced by carbon in a few minutes at 2500°. This is a regular 

 lecture experiment not requiring more than a quarter of an hour. 



By this method we have been able to cause boron and silicon to 

 act on metals, and thus obtain borides and silicides in very 

 beautiful crystals. 



This investigation is being continued. — Com-ptus Rendus, Dec. 12, 

 1892. 



ON THE DAILY VARIATIONS OF GRAVITY. BY M. MASCART. 



I have on former occasions used under the name of a gravity 

 barometer an instrument by which the variation of gravity between 

 different stations may be determined. The apparatus has the 

 drawback of being very fragile, but the same arrangement has 

 great advantages in examining whether there are temporary varia- 

 tions in one and the same place. 



Eor some years past I have arranged a barometric tube contain- 

 ing a column of mercury four metres and a half in length, which 



