1835.] BecquereTs Traitt Experimental, Sfc. 07 



The author divides the work into two parts. In the first division 

 he considers the general properties of the electric principle in rest 

 and motion, as well as those relating to magnetism. In the second, 

 he treats of their relations with chemical affinity, and their applica- 

 tion to phospherescence, to spontaneous actions and other phenomena, 

 which seem to derive their origin from electricity. In the histo- 

 rical preface with which the work commences, three periods are spe- 

 cified as forming distinct eras in the science. 



The first period begins with Thales, 600 years before the Christian 

 era, the first individual as far as we can learn from history, who 

 observed the power of attracting light bodies, which amber acquires 

 when exposed to friction, and terminates with the great discovery of 

 Galvani in 1790. The second period extends from this discovery 

 (inclusive) to 1820, when Oersted demonstrated the intimate con- 

 nexion subsisting between electricity and magnetism. The third 

 period brings the history of electricity and magnetism down to the 

 present day. 



Passing over this division of the treatise, which we consider well 

 worth perusal, we proceed to present a short outline of the applica- 

 tions of electricity to the explanation of natural phenomena. 



Phosphor esence, according to the facts which have been ascer- 

 tained in reference to it, is produced in particular bodies by : 1 . Heat, 

 as occurs in the diamond, when submitted to a considerable tempera- 

 ture, a fact observed by Boyle in 1 663, and in anhydrous nitrate of 

 lime, and likewise in fused muriate of lime. Many other bodies ex- 

 hibit this phenomenon in these circumstances, as shells, sulphate of 

 lime, caustic potash, soda, and chalk. 2. Percussion, as adularia 

 when struck in such a manner as to form fissures in the internal 

 substance chalk. 3. Friction. 4. Exposure to the light of the 

 sun, as in diamonds which lose this property by calcination, tubes 

 of glass, &c. 5. Compression, which excites a luminous appear- 

 ance in all bodies, water especially when compressed in a tube 

 with a piston exhibits this property, and also olive oil, alcohol, ether, 

 acetic acid, sulphur, sulphate of magnesia, nitrate of potash, black 

 oxide of manganese, mica vegetable charcoal, oxygen and common 

 air. According to Pearsall, chlorophane which loses its phospho- 

 rescent property by heat, resumes this quality by exposing it to the 

 action of a Leyden phial. 



This phenomenon, which is familiarly illustrated during the expo- 

 sure to heat of fluor spar in a dark situation, and in the putrefaction 

 of fishes, admits of explanation on the principle that light accom- 

 panies the disengagement of electricity only when the latter possesses 

 sufficient tension, and that it is owing either to the separation of the 

 two electricities at the moment when they are disengaged, or to their 

 action upon the surrounding bodies, in order to form a neutral fluid. 

 When the two electricities separate by friction the chemical action 

 of two bodies which are in contact, it is impossible to collect the two 

 fluids unless the two bodies are not good conductors, because they 

 are so rapidly reinstated, that the two surfaces cannot accumulate 

 enough of electricity to procure for them, on account of the conduct- 

 ing power of the body, enough of tension to produce the luminous 



f2 



