1881.] Radiant Energy into Sonorous Vibrations. 



515 



b. When the black surface was inside, good sounds, 30, were 

 the result. 



c. When the glass was cleaned, the sounds became = 50. 



32. An ebonite plate was similarly treated. 



a. When the blackened surface was outside, sounds = 15 were 

 obtained. 



b. When the blackened surface was inside, the sounds were =3. 

 This being an anomalous result, several experiments were now 



made to test the behaviour of opaque and transparent bodies, when 

 used as disks, for while in the previous experiments the effect was 

 greatest when the blackened surface faced the interior, here we find 

 the opposite result produced, viz., the greatest effect was produced 

 when the blackened surface was on the exterior. 



33. Another ebonite disk 0'6 millim. thick was made dull on both 

 sides by rubbing it with emery paper. It was fixed in case (No. 2), 

 fig. 5, without the lens. 



a. It gave sounds = 15. 



b. It was now blacked on one side, and when that side was 

 turned to the source, it gave sounds = 30. 



c. The unblackened side was turned to the source, and it gave 

 sounds = 15. 



34. A thin glass plate (1*5 millims. thick) — 



a. When clear, gave sounds = 50. 



b. When blackened thinly on one side, and that side turned to 

 the source, it gave sounds = 20. 



c. When blackened thickly on one side and thinly on the other — 



1. Thick side to light, sounds = 0. 



2. Thin side to light, sounds = 20. 



35. A glass plate (3 millims. thick) was blackened on one side. 



a. Black outside, sounds = 2. 



b. ,, inside, ,, = 30. 



36. A clean mica plate (1*2 millims. thick) — 



a. Gave sounds = 30. 



b. When blacked on one side. 



1. Black outside, sounds = 10. 



2. ,, inside, ,, = 30. 



37. Thin copper foil blacked on either side, sounds were nil, 



38. A^ copper disk (0*2 millim. thick) blacked on one side. 



a. Black outside, sounds = 3. 



b. „ inside, ,, =0. 



39. Zinc foil blacked on one side. 



a. Black outside, sounds = 10. 



b. ,, inside, ,, = 3. 



