96 Mr. J. J. Waterston on some Electrical 



both their sides, and between them is placed a cake of beeswax. 

 It quickly takes on positive on both sides, which increases in 

 intensity with the time of exposure. A cake of sealing-wax 

 is similarly influenced. A cake of sulphur also, but much 

 slower. 



41. A 4-inch cake of sulphur is strongly excited on one sur- 

 face, a, and then placed upon three upright sticks of sealing-wax. 

 Induced charges were taken from centre of a, and also from 

 centre of opposite side, j3. The first was 95° X 8N., the second 

 80° x 8 N. Twenty minutes afterwards the first was 85° x 8 N., 

 the second 55° x 8 N. A lighted taper was then held opposite 

 a, which reduced its force to zero, and the force at /3 was then 

 30° x 8 P. Such results could not be obtained from sealing-wax 

 or beeswax-cakes. 



42. The a surface of sulphur cake excited as in 41., and lighted 

 taper immediately afterwards held opposite a. The result was 

 zero both at a and ft. If the taper, instead of being held oppo- 

 site a, be held opposite ft, the plate becomes a charged magic 

 pane without coatings. 



43. A cake of very strongly excited sulphur resting on wax 

 cylinder ; upon it are placed three similar unexcited cakes, b, 

 c } d. After ten seconds theyVere removed and examined sepa- 

 rately at the electroscope ; b was found 60° P., c neutral, d 20° P. 



44. Three cakes of sulphur resting on three sticks of sealing- 

 wax; the lowest excited N. on its upper surface n so as to 

 give induced charge from its centre 90° x 4. After remaining 

 undisturbed for about forty-eight hours, the centre of r, the top 

 surface of upper cake, was found 10° N., and centre of m, 

 the lower surface of first or excited cake, 30° P. The three 

 cakes were then separated, and induced charges taken from both 

 sides of each while it rested by itself on the three sticks of seal- 

 ing-wax (fig. 24). The following was the result : — 



Force at centre of r greater than at centre of q and equal 90° x 2P. 

 Force at centre of o greater than at centre of p and equal 60° N. 

 Force at centre of n 90° x 4 N. 

 Force at centre of m 50° x 4 N. 



45. A cylinder of fine black sealing-wax 2 inches in diameter 

 and 4 inches high, with two small handles of stick wax project- 

 ing at the centre so as to hold it and remove it without touching 

 its surface. It was cleaned with solution of soda, washed with 

 running water, and dried in oven ; when still hot placed it on 

 cap of electroscope ; the insulated B. D. charged positive was 

 placed on its top surface, and leaves diverged to 80° negative. 

 After three minutes took off B. D., the leaves show 60° negative ; 

 then off with cylinder, and leaves fall to zero. Put on cylinder 



