610 THE INSULATING STOOL. 



a stool and placing the outstretched hand on the con- 

 ductor, or holding in his hand one end of a chain of 

 which the other end is suspended from the conductor, 

 may charge his own body with electricity, if the machine 

 is worked by an assistant. Sparks may be drawn from the 

 person on the stand by others, or he may draw sparks 

 from his own body by bringing his finger or a small 

 metal rod, held in the hand, near conducting bodies. 

 The electrified human body manifests phenomena of 

 repulsion and attraction like other electrified bodies ; for 

 example, if the hair of the person standing on the stool 

 is pretty dry, it will more or less completely stand on 

 end, in consequence *of mutual repulsion of different 

 hairs. 



The glass legs of the insulating stool must, of course, be dry ; if 

 necessary, they mnst be dried by friction and warmth. The stool 

 should not be too near the table upon which the machine is placed, 

 that there may be less probability of contact between the table and 

 the clothes of the person standing on the stool. Nor must his 

 clothes, for obvious reasons, touch those of any person near him. 



The dissipation of electricity through the fibres of the clothes, 

 the hairs, and other projecting points, is so considerable that not much 

 electricity can be accumulated in the human body. The sparks 

 drawn are never large. 



An insulating stool need not be specially purchased. It can easily 

 be put together by placing a board, a few decimetres long and wide, 

 upon four strong inverted tumblers, which serve as legs. If the 

 tumblers have not all the same height, a few pieces of cardboard or 

 folded paper, used to fill up any space between tumbler and board, will 

 easily enable the experimenter to stand securely upon the improvised 

 stol, provided that a little caution is used in mounting upon the 

 stool. The tumblers can bear a great load, but the experimenter 

 should at once step gently on to the centre of the board, so as not 

 to push sideways against the tumblers, which might break them. 



No varnishing is recommended when the tumblers are to be used 

 only temporarily, as the varnish cannot be removed without incor.- 

 venience and a rather considerable expenditure of spirit of wine. 

 If it should be found that the insulation is imperfect, their surface 



