in Magnetism and Electricity. 95 



the passage of a tolerably strong current through the coil, yet it 

 was not sufficiently powerful to make the thin wire red-hot 

 at N. 



149. When contact was made between the double coil and 

 the single pair of zinc and platinum plates contained in a glass 

 vessel (102), the passage of a current through the water in the 

 tub was indicated by the liberation of bubbles of hydrogen from 

 the platinum plate, as well as by the deflection of the galvanometer 

 at N. This result was also obtained when the current from the 

 same pair of plates was transmitted through a small double coil 

 of twin conductors (165) immersed in a glass of distilled water. 



150. When the ends A, B of the double coil in the tub, or of 

 the coil in the glass vessel, were connected with the respective 

 terminals of the galvanometer, after all contact with the voltaic 

 couples had been broken, the galvanometer always indicated 

 a strong secondary current from the coils, similar to that 

 observed when the conductors were extended separately in the 

 canal (119). 



151. A quantity of common salt was now dissolved in the tub 

 of fresh water, sufficient to make the solution as nearly as pos- 

 sible of the same specific gravity as sea- water. On repeating 

 the experiments with the naked and tape-covered coils immersed 

 separately in the tub with the planes of the coils 3 inches apart 

 (142), the currents from the 5- and 10-inch intensity-armatures 

 which, when the coils were at the same distance apart in fresh 

 water, would not melt any thin wire at N, now melted 30 inches 

 of iron wire *035 of an inch in diameter, and 6 feet of wire '065 

 of an inch in diameter respectively ; and the current from the 

 2J-inch machine now melted 4 inches of the thin wire (107). 



152. When the tape-covered conductors were again arranged 

 as a double coil of twin conductors, so little resistance was 

 offered to the transmission of the alternating current through 

 the liquid, that the 5- and 10-inch intensity-armatures now 

 melted the maximum quantity of wire at N that they were ca- 

 pable of melting in short circuit ; and the current from a single 

 Grove's cell would now make f of an inch of the thin wire 

 red-hot. 



153. Instead of the bright flash and combustion of the cop- 

 per, which accompanied the interruption of the current from the 

 10-inch intensity-armature on making and breaking contact be- 

 tween the ends C, D of the double coil while dry and suspended 

 in air, a small spark only was visible when it was immersed in 

 salt water, and the thin wire, when introduced between C and D, 

 was not made red-hot. 



154. On substituting dilute sulphuric acid, spec. grav. 1*110, 

 for the salt water in the tub, and transmitting the alternating 



