"To test this theory I took three of the cylindrical armatures fromthe Instrume nt described in yesterdays letter and placed them side by side in the coil.'
"The sound emitted was much louder than any heard before."
"Substituting wrought iron nails for the iron cylinders the soundwas still furth er increased in intensity."
"I altered the pitch of a large tuning fork so as to bringit into unison with th e transmitting Instrument. On inserting its stem in the coil (at the top of a c ylinder and nail)--THE TUNING FORK SOUNDED (Fig. IV). This statement requires v erification as the noise of the machinery rendered the experiment uncertain."
Bell here places the nail between two cylinders--"A CLEARMUSICAL NOTE WAS PRODUC ED SIMILAR IN PITCH TO THE ARMATURE OF THE TRANSMITTING INSTRUMENT AND EQUAL TO IT IN LOUDNESS." When he altered the pitch of the (transmitting) armature, the coil reproduced it exactly. When he moved the transmitting key up and down rapi dly, "the coil reproduced the taps with the UTMOST DISTINCTNESS and with the pit ch due to the transmitting instrument."
Bell intended to put a wrought iron nail inside a bundle of ironwires placed in the core, but found that the nail vibrated laterally, rattling against the wires . Therefore, he removed the wires before conducting the expeirment shown in the next sketch.
Bell inserts two wroght iron nails into the core. The one of the leftis a prot ion of a 'very large nail withch had been broken'. The one on the right was ' an ordinary two inch nail.'
"The upper nail vibrated against the lower one PRODUCING AS CLEAR AND LOUD A MUS ICAL NOTE AS WAS GIVEN OUT BY THE ARRANGEMENT SHOWN IN FIG. V."
Nails of equal size did not produce the note, thought they did make considerable noise.
"A single wrought-iron nail, one end of which was split,produced a faint muscial note VERY HIGH IN PITCH. It seemed to be a harmonic of the generating sound."
It is not clear how Bell is inducing the current in thiscase. We need to check his letter to Hubbard of Nov. 26 for clues (see Dowd).
"After the men in the workshop had left the building I was enabled to hear a crac kling noise very high in pitch proceeding from the core of an electro-magnet. T he sound was very faint and seemed to come in beats.
"I could not discover the connection between its pitch and that of the generatin g Instrument."