364 Prof. Hughes on the Action of Sonorous Vibrations [May 9, 



from each other by a slight space, were electrically connected by laying 

 a similar nail between them, sound could be reproduced. The effect 

 was improved by building up the nails log-hut fashion, into a square 

 configuration, using ten or twenty nails. A piece of steel watch 

 chain acted well. Up to this point the sound or grosser vibrations 

 were alone produced, the finer inflections were missing, or, in other 

 words, the timbre of the voice was wanting, but in the following experi- 

 ments the timbre became more and more perfect until it reached a 

 perfection leaving nothing to be desired. I found that a metallic 

 powder such as the white powder — a mixture of zinc and tin — sold in 

 commerce as " white bronze," and fine metallic filings, introduced at 

 the points of contact, greatly added to the perfection of the result. 



At this point articulate speech became clearly and distinctly repro- 

 duced, together with its timbre, and I found that all that now 

 remained was to discover the best material and form to give to this 

 arrangement its maximum effect. Although I tried all forms of 

 pressure and modes of contact, a lever, a spring ; pressure in a glass 

 tube sealed up while under the influence of strain, so as to maintain 

 the pressure constant, all gave similar and invariable results, but the 

 results varied with the materials used. All metals, however, could be 

 made to produce identical results, provided the division of the metal 

 was small enough, and that the material used does not oxidize by 

 contact with the air filtering through the mass. Thus platinum and 

 mercury are very excellent and unvarying in their results, whilst lead 

 soon becomes of such high resistance, through oxidation upon the 

 surface, as to be of little or no use. A mass of bright round shot is 

 peculiarly sensitive to sound whilst clean, but as the shot soon become 

 coated with oxide this sensitiveness ceases. Carbon again, from its 

 surface being entirely free from oxidation, is excellent, but the best 

 results I have been able to obtain at present have been from mercury 

 in a finely divided state. I took a comparatively porous non-con- 

 ductor, such as the willow charcoal used by artists for sketching, 

 heating it gradually to a white heat and then suddenly plunging it in 

 mercury. The vacua in the pores, caused by the sudden cooling, 

 become filled with innumerable minute globules of mercury, thus, as 

 it were, holding the mercury in a fine state of division. I have also 

 tried carbon treated in a similar manner with and without platinum 

 deposited upon it from the chloride of platinum. I have also found 

 similar effects from the willow charcoal heated in an iron vessel to a 

 white heat, and containing a free portion of tin, zinc, or other easily 

 vaporized metal. Under such conditions the willow carbon will be 

 found to be meiallized, having the metal distributed throughout its 

 pores in a fine state of division. Iron also seems to enter the pores if 

 heated to a white heat without being chemically combined with the 

 carbon as in graphite, and, indeed, some of the best results have been 



