254 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



The mine is shallow, only twenty feet of rock being above it, 

 the accident occurring 130 feet from the month. The man 

 and woman who were killed were at the working face in ad- 

 joining galleries, separated by twelve feet of coal. These 

 two people were practically entirely surrounded by a partial 

 conductor in connection with the earth, affording certainly 

 quite as good protection as the wires Maxwell proposes to 

 place along the edges of a building. 



Plante has applied electricity of high tension for the pur- 

 pose of engraving upon glass. If the surface of a sheet of 

 glass be covered with a thin layer of potassium nitrate in 

 concentrated solution, and this layer be put in communica- 

 tion with one of the electrodes of a secondary battery of 50 

 or 60 cells by means of a wire of platinum round its edges, 

 and the other electrode be a fine platinum wire enclosed in 

 a glass tube, except at its extremity, and held in the hand, 

 then wherever the glass is touched with the platinum point 

 it is permanently engraved. However rapidly the hand is 

 moved, the tracings are clearly engraved on the glass, while 

 if the hand move more slowly, the tracings are more deeply 

 engraved. Either electrode may be used for writing, but 

 the negative requires less current to produce an equal effect. 

 Of course currents from other sources will act in the same 

 way. 



According to Nature, electric lights have become quite 

 numerous in Paris. Eight electric lamps have been placed 

 in the Place de l'Opera, twenty-four in the Opera Avenue, 

 and eight more in the Place du Theatre Francais. Six 

 lamps were lighted for the first time on June 1 on the part 

 of the Palais Bourbon facing the Place de la Concorde. Be- 

 sides this, there should be noticed the private illumination 

 of the Grands Magasins du Louvre, about seventy lamps ; 

 Belle Jardiniere, eight ; Concert de l'Orangerie des Tui- 

 leries, twenty ; and the Hippodrome, thirty-two. This last 

 illumination, being in a closed building, cannot be viewed 

 from the streets. All these illuminations are made by means 

 of the Jablochkoff candle. An electric lamp has also been 

 placed on the top of the Trocadero Palace. 



5. Telephone. 



Gamier and Pollard have described to the French Acad- 



