352 Electrical Resistance of Mixtures of Sulphur and Carton. 



resistance in the air at 17° was found to be 3170 ohms. The 

 rod was immersed in a beaker of turpentine at the same tem- 

 perature, and its resistance almost immediately went up about 

 800 ohms; and in five minutes it was somewhat higher. 

 Though this result did not at first appear to be easily intelli- 

 gible, it is fully explained by supposing that the liquid pene- 

 trated between the sulphur crystals and surrounded the carbon 

 particles. In order to increase the effect, the beaker of tur- 

 pentine containing the rod was placed under the receiver of 

 an air-pump and the air exhausted. After remaining for a 

 quarter of an hour in a vacuum, air was admitted, and another 

 quarter of an hour was allowed for the action of the atmo- 

 spheric pressure. At the expiration of this time its resistance 

 was found to have increased to 15,600 ohms, about five times 

 as great as it was originally. The rod was then placed upon 

 blotting-paper; and three clays afterwards its resistance was 

 2970 ohms, the temperature of the air being 10°. This was 

 200 ohms lower than when it was first made; but the tem- 

 perature was one degree lower. 



Thinking that the oil of turpentine might possibly have had 

 some action on the sulphur, I repeated the experiment with 

 olive-oil. On first immersion, the resistance went up from 

 2970 to 3150 ohms, and in six minutes to 3770 ohms. It 

 was then left in a vacuum for forty-five minutes, after which 

 the air was admitted, though the effervescence had not even 

 then quite ceased ; and when measured, after sufficient interval 

 to allow the oil to penetrate, its resistance had increased to 

 8140 ohms. The comparative smallness of the effect produced 

 in this latter experiment was probably due to the greater vis- 

 cidity of the oil. 



Lastly, since the behaviour of the sulphur-and-graphite 

 mixture under the influence of heat seemed, like that of the 

 microphone, to depend upon the interaction of contiguous 

 particles of carbon, it was expected that one of the sulphur- 

 cells before described might be used as a telephone-transmitter. 

 This, upon trial, was found to be the case. With a single 

 Leclauche the sounds reproduced in the receiving-telephone 

 were feeble ; but well-known nursery-rhymes were easily 

 recognized. When, however, twenty Leclanches were used, 

 the sounds were much louder and the articulation perfectly 

 distinct. No experiments whatever have yet been made with 

 the view of developing this property; and there can be little 

 doubt that it is capable of extension. It is not impossible 

 that a transmitter constructed upon this principle might be 

 found to be of practical value; and it is entirely different, at 

 least in appearance, from any thing which has been made 

 before. 



