126 ANNUAL OF SCIENTIFIC DISCOVERY. 



The mechanical action of a galvanic current may also be referred 

 to its simplest principles by the following proposition : 



4. The force with which an electric tension, present upon both 

 sides of a section of any given fluid, urges the fluid from the positive 

 to the negative side, is equivalent to a hydrostatic pressure which is 

 directly proportionable to that tension. 



In this manner, therefore, we obtain a simple measure of electric ten- 

 sion and its mechanical action in terms of atmospheric pressure, and 

 consequently of gravity. 



The above laws hold good only for fluids of the same nature. When 

 different fluids are subjected to the action of the currents, the mechan- 

 ical action is greatest upon those which oppose the greatest resistance 

 to its passage. The requisite data are still wanting to determine the 

 precise connection between the mechanical action and the resistance ; 

 but observations made with sulphate of copper, of different degrees of 

 concentration, appear to show that the quantities of fluid transferred 

 in equal times by currents of equal intensity, are nearly proportional 

 to the squares of the resistances. 



MAGNETIC SCIENCE. 



AN article in the London Builder, alluding to the discovery made 

 by Mr. George Little, electrical engineer, in which continuous streams 

 of electricity can be produced from single magnets, and be made to 

 decompose water, produce constant power in electro-magnets, and 

 work the chemical printing and double needle telegraph, states that 

 the magnetic science is still in its infancy, and starts the idea that it 

 may be possible to witness such a temporary subversion of the cohesive 

 forces in a deal board, or a stone wall, as would enable a magician like 

 Faraday to pass through it as if it were so much air or so much dust 

 in the sunbeam. 



EXTENSION AND USE OF THE MAGNETIC TELEGRAPH. 



FROM the report of the Superintendent of the U. S Census, and 

 from other sources, we derive the following facts relative to the exten- 

 sion, construction and use of the magnetic telegraph in the United 

 States and elsewhere. The telegraphic system is carried to greater 

 extent in the United States than in any other part of the world ; and 

 the numerous lines now in full operation form a net-work over the 

 length and breadth of the land. The receipts of the " Magnetic Tel- 

 egraph Company " extending from Washington to New York, from 

 its organization in January, 184G, to July, 1852, were $385,641. 

 This company was the first organized in this country and its capital 

 stock is only $370,000. It has six wires from Washington to Phila- 

 delphia, and seven from Philadelphia to New York. The number of 

 messages sent over this line in the six months ending July, 1852, was 

 154,514, producing $68,499 23. It is perhaps the most productive 

 line in the world. 



