604 ELECTRICAL WIND. 



for the present purpose, as well as for several other electrical experi- 

 ments, may be obtained by purchasing at an ironmonger's some 

 1 upholsterer's studs ' used for ornamental work, which are pro- 

 vided with screws or nails for attaching them; the small knobs used by 

 trunkmakers as feet for boxes or trunks and sold at the ironmonger's 

 by the name ' stoolballs ' (see fig. 324, A t page 622), are especially 

 useful. If such a knob be used in the present case, a hole must be 

 made in the cork with the bradawl before the screw of the knob is 

 worked in. 



The discharge through points may be rendered very 

 distinct by means of a wire several decimetres long, 

 ending in a sharp point. The wire being placed in 

 the upper opening of the conductor, with the point 

 upwards, so much electricity is dispersed by the point 

 that the conductor gives now much smaller sparks than 

 before, their length being reduced to one third of what 

 it was without the wire. If the wire is bent, so that 

 the projecting portion is horizontal, and an electroscope 

 is placed at a distance of l m or l m *5 from the point, the 

 electroscope will become charged. 



The electricity thus lost at a point is partially trans- 

 ferred to the particles of air near the point. These 

 become electrified, and as their electricity is of the same 

 kind as that of the point, electrical repulsion must take 

 place. The particles of air fly away from the point, and 

 a small current of air, the 4 electrical wind,' is produced 

 which proceeds from the point. By presenting to the 

 point the flame of a stearine candle, which has a very 

 short wick so as to reduce the size of the flame consider- 

 ably, the flame will be directed aside when the machine 

 is worked, and may even be blown out by the current 

 of air. 



The wire should be rather thick for these experiments> about 3 mm , 

 so that it may not vibrate too much. It is fixed in a cork which 

 fits pretty tight in the opening of the conductor. 



