102 PARTICULAR CONSIDERATIONS ON THE 



vegetable forms. In some, the mimicry is beautiful and com- 

 plete ; for example, in the well-known one called the Arbor 

 Diance. An amalgam of four parts of silver and two of 

 mercury being dissolved in nitric acid, and water equal to 

 thirty weights of the metals being added, a small piece of soft 

 amalgam of silver, suspended in the solution, quickly gathers 

 to itself the particles of the silver of the amalgam, which form 

 upon it a crystallization precisely resembling a shrub. Vege- 

 table figures are also presented in some of the most ordinary 

 appearances of the electric fluid. In the marks caused by 

 positive electricity, or which it leaves in its passage, we see 

 the ramifications of a tree, as well as of its individual leaves ; 

 those of the negative, recal the bulbous or the spreading root, 

 according as they are clumped or divergent. These phenomena 

 seem to indicate that the electric energies have had something 

 to do in determining the forms of plants. That they are 

 intimately connected with vegetable life is indubitable, for 

 germination will not proceed in water charged with negative 

 electricity, while water charged positively greatly favours it ; 

 and a garden sensibly increases in luxuriance when a number 

 of conducting rods are made to terminate in branches over its 

 beds. With regard to the resemblance of the ramifications of the 

 branches and leaves of plants to the traces of the positive electri- 

 city, and that of the roots to the negative, it is a circumstance 

 calling for especial remark, that the atmosphere, particularly 

 its lower strata, is generally charged positively, while the 

 earth is always charged negatively. The correspondence 

 here is curious. A plant thus appears as a thing formed on 

 the basis of a natural electrical operation the brush realized. 

 We can thus suppose the various forms of plants as, imme- 

 diately, the result of a law in electricity, variously affecting 

 them according to their organic character, or respective 

 germinal constituents. In the poplar, the brush is unusually 

 vertical, and little divergent ; the reverse in the beech : in the 

 palm, a pencil has proceeded straight up for a certain distance, 

 radiates there, and turns outwards and downwards ; and so 

 on. We can here see at least traces of secondary means by 



