NATURAL PHILOSOPHY. 169 



of a second to make its journey. From a voltaic sand-battery of twelve 

 pairs of four-inch plates, the current took forty-four hundrcdths of a second 

 to traverse 600 miles of wire. 



Yet again ; currents of a different quality travelled with different degrees 

 of velocity, even when equal to mechanical tasks of like amount at the ex- 

 tremity of any given wire. Seventy-two pairs of sand-battery plates, (each 

 sixteen square inches in area), which lifted 1,400 grains in the magneto-elec- 

 trometer at the end of a 600 miles wire, generated a current which took 

 forty-four hundredths of a second to traverse that distance. Two large 

 double induction coils, thirty-six inches long, (the secondary coils being 

 composed of a mile and a third of fine wire), and excited by ten pairs of 

 plates of 100 square inches each, arranged as a Smee's battery, gave rise to 

 a current which could only lift 745 grains at the end of a 600 miles wire, 

 but the current in this case travelled through the entire stretch of wire in 

 nineteen-hundredths of a second. Simple voltaic electricity was capable of 

 a greater mechanical effort at the end of a long wire, than a magneto-elec- 

 tric current ; but the voltaic electricity, which was capable of the greater 

 mechanical effort, strange to say, travelled through the insulated wire at a con- 

 siderably lower rate of speed. A very large number of experiments com- 

 bined to prove that a rate of transmission could be obtained by the employ- 

 ment of magneto-electric currents from two and a half to three times as 

 great as that of any voltaic impulse that could be used. The mean or 

 average speed for voltaic electricity in a number sixteen gauge copper wire, 

 of a certain determinate length, was about 1,400 miles per second ; the mean 

 or average speed of the magneto-electric current in a similar wire of equal 

 length was about 4,300 miles per second. The maximum speed attained by 

 voltaic electricity was 1,800 miles per second; the maximum for the mag- 

 neto-electric current was 6,000 miles per second. There could be no doubt, 

 after these experiments, that the magneto-electric current issuing from induction 

 coils gives a treble velocity of electrical transmission, and therefore realizes a three- 

 fold working speed. 



Professor Faraday has shown that no augmentation of velocity results 

 from the use of an increased amount of battery-power in the simple voltaic 

 arrangement, up to the employment of twenty times the number of plates 

 used at the first. In this particular again the double induction current es- 

 tablished for itself a marked superiority. This current can have the speed 

 augmented by increased amount of battcrv power. This was remarkably 



/ *< J / 



proved by an inverse inference in one observation, in which there was a 

 steady and gradual diminution of velocity from 5,400 to 3,600 miles per 

 second, during the spontaneous exhaustion of a small Grove's battery, em- 

 ployed in exciting a series of magnetic induction coils. Increased quantity 

 in this arrangement tells by filling the thick wire of the primary coil to its 

 full capacity, and this produces increased polar force in the temporary mag- 

 net, and increased inductive excitement in the finer secondary coil. 



Experiment demonstrates that the velocity of an electric current dimin- 

 ishes with progress along a lengthened gutta percha coated wire, more 

 nearly in the proportion of an arithmetical series, than in that of the squares 



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