124 ANNUAL OF SCIENTIFIC DISCOVERY. 







gas liberated rises constantly to the surface in large heads. The deposit, 

 however, is made with perfect regularity and uniformity. 



PROTECTION OF SILVERED SURFACES- 



Baron von Liebig has patented certain improvements in protecting: the sil- 

 vered surfaces of mirrors and other articles of glass. This method consists 

 in preparing the silvered surface, by depositing thereon a coating of copper, 

 gold, or other metal, by electro-galvanic action, combined with the use of a 

 neutral solution of the double salt tartrate of the oxide of copper, and soda, 

 potash, or ammonia. 



DURABILITY OF ELECTROTYPE WORK. 



Mr. E. Richardson, in a communication to the Builder, London, gives the 

 following information as to the probable durability of electrotype metal, and 

 its thickness. Mr. Richardson states that in 1844, being called upon to fur- 

 nish metal medallions, etc., for the granite testimonial to General Sir Alex- 

 ander Dickson, on Woolwich-common, a very exposed situation, he sug- 

 gested electrotype castings. A consultation of officers on the question fol- 

 lowed, the results being full permission to reproduce the models in electro- 

 type copper, which was ably executed. These castings were at that time of 

 unusual size and thickness, namely, two feet six inches diameter, and fully 

 an eighth of an inch thick of solid metal. This was effected also without 

 sin-inking, and every tool-touch from the clay model was reproduced. These 

 works have been now exposed for fifteen years. They weighed, Mr. Rich- 

 ardson believes, thirty pounds each. No chasing was required. 



On the other hand, Mr. Richardson has had for years a small brass, about 

 fifteen inches high, produced by the old fire-process, which, cost pounds to 

 chase, obliterating every line of his original model, and weighing nearly a 

 quarter of a hundredweight. 



NEW APPLICATION OF ELECTRO-METALLURGY. 



Among the recent applications of electro-metallurgy we may instance the 

 happy idea of Mr. Gaudin of employing it in setting jewels. This is a very 

 delicate and expensive branch of jewelry, and so difficult that the setting of 

 a jewel can seldom be fully relied upon. The inventor first takes a mould in 

 wax of the ornament that is to receive the jewels, then places on it, at the 

 proper points, the jewels, embedded in the wax to a sufficient depth; the 

 wax model, rendered a conductor of electricity, is placed in the gold solu- 

 tion, and the metal deposited upon it. When the deposit is completed, the 

 jewel is found firmly enchased in the metal, from which, if the process has 

 been properly conducted, it will be impossible for the jewel to escape. The 

 saving of time effected by this process is also very considerable. By the or- 

 dinary process a jeweller can scarcely set sixty jewels in a day, but by the 

 new process he can set as many as fifteen hundred to two thousand in a 

 day. 



LAST OF THE ATLANTIC CABLE. 



During the past summer, several attempts have been made to elevate and 

 recover the American end of the Transatlantic telegraph ; but in every in- 



