264 MEMORIAL OF JOSEPH HENRY. 



In the course of 24 hours a globule of mercury was found at the 

 lower end of the lead rod; and in five or six days it had all passed 

 over excepting what appeared in the form of crystals of a lead 

 amalgam in the upper vessel. * A long piece of thick lead wire 

 was afterward suspended in a vertical position, with its lower end 

 dipping into a cup of mercury. In the course of a few days, traces 

 of the mercury were found in the rod at the height of three feet 

 above the cup : thus showing that a metal impervious to water or 

 oil (excepting under very great pressure) was easily penetrated to 

 great distances by a liquid metal. 



Some years later on a visit to Philadelphia he endeavored with 

 the assistance of his friend Dr. Patterson (then Director of the 

 United States Mint), by melting a small globule of gold on a plate 

 of clean sheet-iron, to obtain its capillary absorption ; but without 

 effect; probably owing to the interposition of a thin film of oxide. 

 Applying to another personal friend, Mr. Cornelius of Philadelphia, 

 a very intelligent and ingenious manufacturer of bronzes, and plated 

 ornaments for chandeliers, etc. to try whether a piece of silver-plated 

 copper heated to the melting point of silver would show any absorp- 

 tion of that metal, he learned that it was a common experience under 

 such circumstances to find the silver disappear; but that this had 

 always been attributed to a volatilization of the silver, or in the 

 workman's phrase, to its being "burnt off." At Henry's request 

 the experiment was tried : the heated end of a silver-plated piece 

 of copper exhibited on cooling and cleaning, a copper surface ; the 

 other end remaining unchanged. Henry next had the copper sur- 

 face slightly dissolved off by immersion for a few minutes in a 

 solution of muriate of zinc, when as he had anticipated, the silver 

 was again exposed, having penetrated to but a, very short and toler- 

 ably uniform distance below the original surface, f 



In 1844, he made some important observations on the cohesion 

 of liquids. Notwithstanding that Dr. Young early in the century 

 maintained that "the immediate cause of solidity as distinguished 

 from liquidity is the lateral adhesion of the particles to each other," 

 and had shown that "the resistance of ice to extension or com- 



* Proceed. Am. Phil. Soc. vol. i. p. 82. 



t Proceed. Am. Phil. Soc. June 20, 1845, vol. iv. p. 177. 



