196 FRICTION AL ELECTRICITY. 



il. 



FRICTIONAL ELECTRICITY. 



322. Preparatory. Provide two stout sticks of sealing-wax 

 and one or two pieces of flannel folded into pads about 20 em. 

 (8 inches) square ; two stout glass tubes closed at one end, 30 or 

 40 cm. in length and about 2 cm. in diameter (long " ignition tubes ") 

 and one or two silk pads about 20 cm. square, the pads being three 

 or four layers thick ; a few pith balls about 1 cm. diameter (whittle 

 them nearly round and finish by rolling them between the palms 

 of the hands) ; a balanced straw about a foot Q ^ 

 long, represented in Fig. 185. The ends of the ' 



straw carry two small discs of paper (bright ~ IG " T ^' 



colors preferable) fastened on by sealing-wax. The cap at the mid- 

 dle of the straw is a short piece of straw fastened by sealing-wax. 

 This is supported upon the point of a sewing-needle, the other end 

 of which is stuck upright into the cork of a small glass vial. From 

 the ceiling or other convenient support, suspend one of the pith 

 balls by a fine silk thread. The efficiency of the silk pad above 

 mentioned may be increased by smearing one side with lard and 

 applying an amalgam made of one weight of tin, two of zinc, and 

 six of mercury. The amalgam which may be scraped from bits of 

 a broken looking-glass answers the purpose admirably. 



323. Electric Attractions. See that the sealing- 

 wax and glass rods, the flannel and silk pads are perfectly 

 dry. Have them quite warm, that they may not condense 

 moisture from the atmosphere. For a moment hriskly rub 

 the sealing-wax with the flannel and bring the stick near 

 the suspended pith ball. The ball will be drawn to the 

 wax. Bring the wax near one end of the balanced straw ; 

 it may be made to follow the wax round and round. 

 Bring it near small scraps of paper, shreds of cotton and 

 silk, feathers and gold leaf, bran and sawdust, and other 

 light bodies; notice that they are attracted to the wax. 



