94 SCIOPTICON MANUAL. 



EIPPLE WAVES. Fill the tank, as it rests on the ver- 

 tical lantern, with clear water, when taps on the edge 

 of the glass will start ripple waves, which will be seen 

 on the screen in varied harmonious arrangements of form. 



Touching the surface with the point of a fine wire 

 will start the waves in circles. Vibrations effected by 

 drawing a fiddle bow across the edge are seen to vary 

 according to the different tones produced. 



ADHESION FIGURES. Drops of various oils upon the 

 surface of the water, essential oils for instance, will ex- 

 hibit various interesting adhesion figures, each oil as- 

 suming some peculiar form of outline. 



MAGNETIC CURVES. A thin bit of magnetic steel, say 

 three-fourths of an inch long by one-eighth wide, ce- 

 mented on the under side of a glass plate, will attract 

 fine iron filings scattered upon the plate into curves, 

 illustrating the deviation of the magnetic attraction at 

 either pole and the neutral axis in the centre of the 

 magnet. A few taps on the glass will assist the arrange- 

 ment. 



CHAPTER VIII. 



CONCERT EXERCISES. 



THE value of visible illustrations as a means of im- 

 parting instruction, and of affording rational entertain- 

 ment, depends much on the accompanying oral explana- 

 tions. 



