172 ANNUAL OF SCIENTIFIC DISCOVERY. 



tions, % mixture of two-thirds hydrochloric and one-third nitric 

 acids, or three-fifths of the former and two-fifths of the latter, will 

 easily dissolve gold and platinum, but will only superficially 

 attack pure silver, a superficial chloride being formed, protect- 

 ing the rest of the silver like a varnish, for any length of time ; if 

 copper be present, the metal is attacked. He therefore makes a 

 new battery in which pure silver in aqua regia replaces the pla- 

 tinum or carbon in the nitric acid of a Grove or Bunsen cell ; 

 after several months' use, the silver was not sensibly diminished 

 in volume, and no chloride of silver was found in the porous cell. 

 He considers it more constant than Bunsen's battery. 



Improved Bunsen Battery. M. Zaliwski uses two porous ves- 

 sels, one within the other. In the inner one, which contains the 

 carbon, he puts nitric acid, and in the outer sulphuric acid ; in the 

 outer vessel, containing the zinc, he places a solution of sal am- 

 moniac. No effervescence, it is said, takes place, and no zinc is 

 uselessly consumed. 



Velocity of the Electric Current in the Atlantic Cable. In ascer- 

 taining the exact longitude by means of the Atlantic telegraph 

 cable, a distance of about 1,900 miles has been measured, and the 

 measure is probably not more than 40 feet from the truth. The 

 time required for a signal to pass through the cable" has been dis- 

 covered with still greater precision to be thirty-one one-hundredths 

 of a second, which is probably not in error by one one-hundredth 

 of a second. This is equivalent to a velocity of 6,020 miles a sec- 

 ond, and is notably less than the velocity of the electric fluid upon 

 land lines, which numerous observations have shown to average 

 16,000 miles a second. 



On Saturday, Dec. 21, 1867, a message of 48 words of greeting 

 was sent from the Royal Polytechnic Institution, London, to the 

 President of the United States at Washington. The total time of 

 transmission was 9^ minutes, divided as follows : from London to 

 Heart's Content, 4 minutes ; from Heart's Content to Plaister 

 Cove, 1^ minutes ; at Plaister Cove one-half minute ; PlaisterCove 

 to New York, 1 minutes; New York to Washington, 1 minutes. 

 A reply of 60 words was sent back from Washington to London in 

 20 minutes. On the same evening, a message of 22 words was 

 sent from London to Heart's Content, and in 10 minutes a reply 

 of 24 words was delivered in London. 



Velocity of Sound. M. Dulong, on causing organ-pipes to 

 sound by means of different gases, found that the velocity of 

 sound at zero was as follows : Carbonic acid, 856 feet in a second ; 

 oxygen, 1,040 feet; air, 1,093 feet; hydrogen, 4,163 feet. 



Refraction of Sound. The most notable observation lately 

 made in the direction of reducing sound to form and measure, is 

 the refraction of it by M. Sondhaus, by means of acoustic lenses 

 made of spherical collodion envelopes filled with carbonic acid. 



COHESIVE FORCE OF SEALING-WAX. 



The cohesive force of the best red sealing-wax has been proved 

 to be equal to 1,500 pounds per square inch, and that of the black 



