398 Intelligence and Miscellaneous Articles, 



thus during the inundations of the plains of the Saone, Bcarcely per- 

 ceptible cuiTents were obtained by establishing a metallic communi- 

 cation between the Saone and the soils which had just been inun- 

 dated. In salt marshes, as must have been expected, the soil is ne- 

 gative in relation to fresh waters. 



I have found that the electromotive force produced by the contact 

 of sea-water and vegetable mould is, ccBteris paribus, about 2'4 

 stronger than that which is produced by the contact of the same 

 soils and fresh waters. 



These experiments were followed night and day last winter at the 

 Jardin des Plantes, by putting the water of one of the wells of the 

 establishment in communication with the surrounding earth. Varia- 

 tions and inversions in the direction of the current were proved, due 

 to the infiltration of waters containing substances, which are not 

 always of the same nature, into the wells of large towns. 



Third Part. On Terrestrial Couples with constant currents. — Expe- 

 rience having shown that the results could only be depended upon 

 when the electrodes prepared with charcoal had been placed for 

 several days in contact with the soils and waters, I found myself 

 compelled in the course of last summer to establish an observatory 

 in a locality of the department of Loiret, where I collected a great 

 part of the materials contained in the memoir which I now present 

 to the Academy. 



. On comparing the terrestrial couple composed of salt water of 3°, 

 good vegetable mould, and two coke electrodes, with a couple with 

 sulphate of copper, it was found that the electromotive force obtained 

 with sea- water or salt water is 0*45 of that of the latter couple ; this 

 consisted of a glass vessel containing a saturated solution of sulphate 

 of copper and a plate of copper, and of an immersed diaphragm of 

 unglazed porcelain containing water acidulated with one-tenth of 

 sulphuric acid, and a cylinder of amalgamated zinc. By employing 

 as electrodes, coke covered with peroxide of manganese, this force 

 becomes five times as great ; the peroxide of manganese acts by 

 removing the hydrogen which is deposited on the negative electrode, 

 which causes a current in the same direction as the terrestrial cur- 

 rent. The electromotive force at the contact of water and vegetable 

 mould is the tenth of that of the couple formed of amalgamated zinc 

 immersed in fresh water and charcoal in contact with vegetable 

 mould. 



The composite terrestrial couple, formed of salt water of 3° in 

 which a plate of amalgamated zinc is immersed, and of vegetable 

 mould in contact with a plate of manganized charcoal, has an elec- 

 trom-otive force represented by 0*52, that of the couple with sulphate 

 of copper being represented by 0*579, and that of the couple with 

 nitric acid by TO. This couple was that of Grove, formed of a dia- 

 phragm of 4 centims. in length and 2 in diameter, and an electrode 

 of platinum 4 centims. in length and breadth. The diaphragm con- 

 tained acidulated water (one-tenth) in which a little cylinder of 

 amalgamated zinc was immersed. 



The constancy of the current of this composite terrestrial couple 



