Properties of Bees' -wax and Lead Chloride. 133 



For the last two years my attention has been turned to wax 

 as a good material for electrically testing, especially in regard 

 to the connexion which, in our paper on the Viscosity of 

 Dielectrics, communicated to the Royal Society, we pointed 

 out existed between high specific inductive capacity and low 

 specific resistance. I therefore had constructed a large con- 

 denser, consisting of many sheets of letter-paper soaked 

 in melted bees'-wax, with alternate sheets of tin -foil. After 

 the condenser was built up in the usual way, melted bees'-wax 

 was poured in, the plates squeezed together, and the whole 

 shut up in a fairly good water-tight wooden box. The con- 

 denser was buried several feet under ground, to ensure uni- 

 formity of temperature, connexion being made with the insu- 

 lated coating by a piece of Atlantic-cable core, and with the 

 other coating by a piece of bare copper wire. 



After this condenser had been buried for a short time 

 underground, it showed the apparently abnormal condition 

 of diminution of resistance by electrification. This pheno- 

 menon then formed the subject for special investigation 

 with this condenser, an account of the results obtained being 

 given at the end of this short paper. 



As bees'-wax is one of the few substances in which the 

 index of refraction for light increases in passing from the 

 liquid to the solid state, it seemed important, in connexion 

 with the electromagnetic theory of light, to carefully mea- 

 sure the specific inductive capacity of a wax condenser as 

 it was gradually cooled through the solidifying point. A 

 small, shallow, clean copper box, 19 centims. long by 17 

 centims. wide, was therefore lined with a sheet of letter-paper, 

 0*036 centim. thick, previously well soaked in melted bees'- 

 wax. A clean copper disk, 12*8 centims. in diameter, was 

 placed on the top, weighted down, and the dish filled 

 up with melted wax. This condenser, AB (fig. 1), was 

 heated in an oil-bath, CD. E and F are holes for the 

 insertion of thermometers, of which the bulbs were just 

 above the wax condenser ; Gr is an opening through 

 which the insulated electrode H of the condenser may pro- 

 trude without touching the oil-bath. A wooden stand, W W, 

 supports the condenser in the middle of the bath ; and a glass 

 vessel V holds strong sulphuric acid to keep the inside space 

 artificially dry. The bath is closed by a double door, which 

 is made to fit well by a strip of leather inserted between it 

 and the bath. 



The condenser having been inserted, the bath was heated to 

 about 90° C, and kept at that temperature for some time ; the 

 lamps were then removed, when the temperature fell very 



