872 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



with the Jerusalem artichoke, a species of sunflower having tubers 

 like potatoes — the word Jerusalem being a corruption of the Italian 

 girasole, meaning sunflower. In this country the artichoke proper 

 has been cultivated to a ver}^ limited extent, but in Europe, par- 

 ticularly in the southern part of it, the plant is very generally in 

 use. It resembles a thistle, and has large, scaly heads, like the 

 cone of the pine tree ; the fleshy base of these scales, which is the 

 receptacle of the flower, is the most palatable part of the plant. 



Absorption of Hydrogen by Copper. 

 It is well known that a definite but very unstable compound 

 may be formed, containing two atoms of copper to one of hydro- 

 crcn, by heating a mixture of sulphate of copper with hypophos- 

 phorous acid. This compound cannot be formed by the direct 

 action of the two elements upon each other, but M. Caron has 

 lately shown that hydrogen gas may be imprisoned in the melted 

 copper. A small bar of copper was put into a porcelain crucible, 

 introduced into a tube of the same material, raised to a tempera- 

 ture somewhat higher than that at which copper fuses, while a 

 current of hydrogen gas was driven through it. At the end of the 

 tube by which the gas made its exit, a glass balloon, with two wide 

 tablatures, was placed to enable the observer to see what was 

 woino- on within the apparatus. So long as the metal remained 

 in a solid state nothing occurred. But the moment it began to 

 inelt numerous bubbles rose on its surface, and a considerable 

 quantity of steam was condensed in the balloon. This M. Caron 

 explains by supposing that even the best copper contains a little 

 oxide, and that during its fusion the oxygen is expelled, and com- 

 binino- with hydrogen, forms water. After the operation, the 

 ino-ot of copper was examined, and found to contain numerous 

 cavities filled with hydrogen gas ; whence it may be concluded 

 that copper, in a state of fusion, absorbs hydrogen. 



Colors from Artificial Light, 



Prof. Nickles, of France, makes, in SilUman^s Journal, some 

 interesting observations regarding colors, to which he was led by 

 first noticing that a certain chemical compound, known to be green 

 by daylight, was, in the eyening, black. He substituted for his 

 o-asli'ht an oil lamp, and afterward a wax candle, but the com- 

 pound still appeared black. Under the flame of magnesium, how- 

 ever, the green color reappeared, showing that burning magne- 



