168 ANNUAL OF SCIENTIFIC BISCOYERY. 



Africa he stated he had two plans in contemplation for its extension to 

 Egypt one, a line dropped in the Mediterranean, in the shallow line near 

 the coast, and another buried in the sand along the shore, both of which 

 he was satisfied might be laid secure from derangement of any kind. He 

 then concluded with a statement of the labor and attention he had given 

 for many years in preparing for the telegraph to America, and of the 

 depth, on the proposed line, as recently ascertained by Lieut. Maury, of 

 the United States, with some estimates of the weight and cost, and stated 

 that a return of 100/. to 1501. per day would give a fair interest on the 

 necessary capital ; that his plan comprised several lines of communication ; 

 and that he entirely deprecated the idea of a single line of communication, 

 which he believed could not be done. 



ELECTRIZATION BY INFLUENCE. 



The French Academy has recently received a memoir of great interest 

 from M. Melloni, on the subject of electrization by influence. The 

 hypothesis which has hitherto prevailed to explain the general character of 

 the phenomena relative to static electricity consists in admitting the exist- 

 ence of two imponderable principles, of two fluids endowed with reciprocal 

 attraction each for the other, and with repulsion for themselves ; and by 

 this way the speculative philosopher obtains two agents possessing opposed 

 properties, and susceptible under many circumstances of being disguised, 

 or of being concealed by each other. At the first they were called vitreous 

 and resinous electricity ; and then, to exhibit more forcibly the antagonism 

 of the way by which they acted, they were styled positive and negative 

 electricity. No data having fallen into the philosopher's hands that might 

 authorize him to define the absolute quantities of -these fluids which might 

 exist together in bodies, it has been supposed that ponderable matter 

 contained infinite quantities of them, or at the least, quantities which may be 

 regarded as infinite in comparison with the amount that may be excited in 

 experiments. Notwithstanding this inexhaustible quantity of fluids 

 contained in bodies, it suffices that one or the other is in the predominance 

 to urge it to the surface, and to exhibit there the properties which are 

 peculiar to it. This accumulation of the fluid in excess on the exterior 

 surface constitutes the phenomenon, of electrization. Consequently a 

 body may be electrified by two different and opposite manners, as one or 

 the other fluid predominates on its surface ; in every case, the fluid in 

 excess will exercise to escape a pressure, which is " electrical tension," 

 properly so called. When the tension is great enough, the electricity 

 appears in the form of a spark, whose dimensions may vary in enormous 

 proportions. Between the phosphorescent sparkling of the stick of 

 sealing wax raoidly rubbed and the dazzling lightning which rends our 



*< o o 



temples in sunder there is no difference other than a difference in degree. 



The explosion of the spark is invariably preceded by electrization by 



influence, a so important phenomenon as to warrant some explanations. 



