GALVANISM. 355 



quillize their fears. Possibly such vindication may be called for by a portion 

 of the present generation having pretensions sufficient to raise them to the 

 .level of envy, but wanting those better qualities which would elevate them ] 

 above it. Certainly no such apology will be needful with posterity. 



The strong affinities of these new metals for one or other of the constituents < 

 of almost every body with which they were brought in contact, and of every i 

 menstruum or atmosphere with which they could be surrounded, was very em- \ 

 barrassing, and rendered the examination of their physical properties extremely 

 difficult. It was found most convenient, either to preserve them in a tube pro- 

 tected from the contact of the air above recently distilled naphtha, or to allow 

 them to combine with mercury so as to form an amalgam, and in that state to 

 preserve them, separating them by heat when the pure metal was required. 



The analogy suggested by the decomposition of the fixed alkalies naturally 

 led to a like inquiry with respect to the earths which enjoy with the former 

 common properties, and those which seemed most analogous to the alkalies. 

 Baryta, strontia, lime, and magnesia, were tried by like methods, but without 

 any satisfactory result. Being slightly moistened at their surfaces, they were 

 exposed to the electric current transmitted by iron wire under naphtha. At 

 the negative pole they assumed a darker color, and small particles appeared 

 there, showing metallic lustre, and which gradually whitened by exposure to 

 air. In the experiments on potassium it was found that when a mixture of 

 potash and the oxide of mercury, tin, or lead, was exposed to the Voltaic cur- 

 rent, decomposition ensued, and an amalgam of potassium was produced. The 

 same method was accordingly tried with the alkaline earths. Mixtures of 

 these substances with oxides of tin, lead, silver, and mercury, were exposed 

 to the current. In these cases, a small quantity of a substance having the 

 whiteness of silver was deposited at the negative pole, which was found to be 

 an amalgam. Still the results were not conclusive or satisfactory. 



The labors of Davy had attained this point when, in June, 1808, he re- 

 ceived a letter from M. Berzilius, informing him that, assisted by Dr. Pontin, 

 that chemist had succeeded in decomposing baryta and lime, by exposing them 

 in contact with mercury to the current. Davy immediately repeated the ex- 

 J periment, and obtained the amalgam of the metallic base of baryta at the neg- 

 ) ative pole. This was accomplished by a battery of 500 pairs, weakly charged, 

 ] acting on a surface of slightly moistened baryta through the medium of a glob- 

 ule of mercury. The mercury gradually became less fluid, and, after a few 

 minutes, was found covered with a white film of baryta ; and when the amal- 

 gam was thrown into water, the latter was decomposed, hydrogen was dis- 

 missed, mercury precipitated, and a solution of baryta formed. A like process 

 gave a similar result with lime. 



Having thus verified the results obtained by Berzelius, Davy extended the 

 same method to strontia and magnesia. The former readily yielded ; the lat- 

 ter was more intractable. By continuing the process, however, for a longer 

 time, and keeping the earth continually moist, at last a combination of the basis 

 with mercury was obtained, which slowly produced magnesia by absorption of 

 oxygen from the air, or by decomposing water. 



Thus were discovered BARIUM, STRONTIUM, CALCIUM, and MAGNESIUM, as 

 an immediate consequence of the first great step made in this course of investi- 

 gation by the discovery of potassium and sodium. 



The next group of earths brought to trial consisted of alumina, silica, zirco- 

 nia, and glucinia, which proved more refractory than any of the former. Driven 

 in search of other methods of experimenting, he considered minutely their 

 qualities in relation to other bodies, with a view to the discovery of analogies / 

 by which his researches might be conducted. From the absence of any ten- j 



