146 Analyses of Boohs. [Feb. 



of copper is soldered to the extremities of a bismuth or antimony 

 cylinder, if heat be applied to one of the solderings, an electric 

 current is established which proceeds from the bismuth to the copper, 

 or from the copper to the antimony, according to the apparatus 

 employed. When circuits are formed with wires of different metals, 

 and the temperature of one of the solderings is elevated successively, 

 currents are produced which indicate an arrangement of the metals 

 according to have thermo-electric properties to be bismuth, platinum, 

 lead, tin, copper, gold, silver, zinc, iron, and antimony, which is 

 analogous to the order of their specific heats. In most of the metallic 

 circuits the intensity of the current is in proportion to the tempera- 

 ture up to 40° at least. 



Some minerals exhibit thermo-electrical properties. In the tour- 

 maline these may be excited by slow heating and cooling, or by rapid 

 heating aud cooling. These vary, according to Becquerel, however, 

 in proportion to the size of the crystals, as the smallest tourmalines 

 assume a very strong polarity by feeble changes of temperature, 

 while Mr. Forbes has concluded from his experiments, that the size 

 of the section of the tourmaline employed has so much influence that 

 where the difference is considerable the largest crystal always is most 

 powerful. A crystal 1 \ inch in length possessed an intensity of 45°. 

 When broken at \ of its length, the two portions being heated and again 

 subjected to experiment, the largest portion indicated a deviation of 47° 

 and the smallest 43°. Mr. Forbes conceives that we may infer from 

 analogy that the intensity increases with the diameter of the tourmaline, 

 but that we are still ignorant if the length of the crystal has any in- 

 fluence on the electrical properties. Canton, Brard, and Haiiy, have 

 observed similar properties in other minerals, and Sir David Brewster 

 has announced them in above 35 bodies, consisting of minerals and 

 salts. He employed for detecting the pyro-electricity small portions 

 of the internal membrane of the arundo phragmites, which, when 

 dry, are extremely light, and adhere to the crystal which has been 

 heated to the number of 1, 2, and 3. Becquerel considers this test 

 insufficient, and affirms that the only criterion by which we can 

 decide upon electrical influence is, first, by the attraction of light 

 bodies presented to the electricity, and second, their repulsion suc- 

 ceeding the contact. 



Heat diminishes the electrical conduction of metals, while it in- 

 creases this property in glass, gumlac, and other bad conductors, but 

 in what way has not been clearly made out. 



2. The author enters into the consideration of the electricity 

 produced by chemical action, as when one body combines with another, 

 the substance acting the part of the acid becomes positively electrical, 

 while the alkali is negative; when one solution acts upon another; 

 when metals react upon acids or saline solutions ; when two different 

 metals react upon one or more liquids, for instance, if a plate of copper 

 and one of zinc, communicating each with one of the ends of the wire 

 of a multiplier, be immersed in a solution of sulphate of zinc, the copper 

 becomes positive and the zinc negative. 3. A review is then taken 

 of the experiments of Pouillet, in reference to the developement of 

 of electricity in combustion. Charcoal, when burned, was found, by 

 that experimenter, to emit positive electricity in the carbonic acid, 



