

505 



elements of lafge surface the amplitude of the vibrations is small 

 and the sound high, whilst with the current from the many ele- 

 ments of small surface the amplitude of the vibrations is large and 

 the sound base. These differences in the vibrations and sounds are 

 still more conspicuous if a galvanometer of small resistance (i. e. with 

 a short and thick wire) is substituted for the voltameter, and about 

 four Smee's elements employed instead of the eight. In each of 

 these experiments the voltameter (or galvanometer) is in the circuit 

 with the cyanide solution ; the quantities of the two currents are 

 made equal by suitably adjusting the relative depths of immersion of 

 the plates of the two batteries ; and each experiment (with the volta- 

 meter) occupies 3 minutes. The size of the mercury electrodes hag 

 also been previously adjusted to the power of the current, so as to 

 give continuous definite vibrations and sounds. 



3. Further : If a current from two Grove's or five Smee's ele- 

 ments of large surface is passed through a primary coil of about 

 250 feet of thick copper wire, through the cyanide solution and 

 small-resistance galvanometer, the vibrations are moderate in size 

 and the pitch of the sound is moderately high ; but if the axis of the 

 coil contains a massive bundle of soft iron wires, the vibrations are 

 much larger and the pitch of the sound is much more base ; and if 

 the primary coil is surrounded by a secondary coil containing about 

 4000 feet of fine copper wire, the ends of which are closely united 

 together, and the iron core is absent, the vibrations are very much 

 smaller and the sound is much higher. In each case the quantify 

 of the current, however, remains the same. If a voltameter is used 

 instead of the galvanometer, a greater number of elements (about 

 eight Smee's) must be employed, and the difference in the effects is 

 then less striking. If a battery of much greater intensity, say 

 twenty Smee's elements, is employed, no difference in the vibrations 

 or sounds is produced by the introduction of the soft iron core, nor 

 by closing the secondary coil. 



Do not voltaic currents therefore of equal quantities* from 

 different sources, or under different external conditions, like heat 

 and light from different sources, possess different qualities 1 



4. From these results (as well as from additional ones that I have 



* I employ the word " quantity " in its ordinary sense, viz. as that indicated 

 by measurement of gases from decomposition of water in a voltameter. 



