C. GENERAL PHYSICS. 179 



cobalt, all take mercury under the same conditions as iron. 

 Aluminum, however, shortly after amalgamation, becomes 

 hot, the mercury seems to boil, and the aluminum remains 

 covered with a chalky crust, on removing which the metal 

 is found beneath without a sign of amalgamation. Proc. 

 Am, Chem. Soc, L, 1876, 49. 



MUSICAL SAND. 



In a communication to the California Academy of Sciences, 

 Frink has stated that in order to ascertain, if possible, the 

 cause of the sound that is produced by the musical sand from 

 Kauai, previously exhibited to the Academy, he had inves- 

 tigated its structure under the microscope, and believed that 

 the facts he had ascertained fully explain the manner in 

 which the sound is produced. As the grains of sand, though 

 small, are quite opaque, it was necessary to prepare them so 

 that they should be sufficiently transparent to render their 

 structure visible. This was efiected by fastening them to a 

 glass slide, and grinding them down until one flat surface was 

 obtained. The grains were found to be chiefly composed of 

 portions of small coral and apparently calcareous sponges, 

 and presented under the microscope a most interesting ob- 

 ject. The sand contained small black particles, which the 

 microscope showed to be formed principally of crystals of 

 nepheline and magnetic oxide of iron, imbedded in a glassy 

 matrix. These were undoubtedly volcanic sands. The struct- 

 ure of these grains, Frink thinks, explains the reason why 

 sound is emitted when they are set in motion. The motion 

 ao-ainst one another causes vibrations in their substance, and 

 consequently in the sides of the cavities they contain ; and 

 these vibrations being communicated to the air by the cavi- 

 ties under the most favorable conditions for producing sound, 

 the result is the loud noise which is caused when any large 

 mass of sand is set in motion. Proc. Cal. Acad. /Sci., 1876. 



CAUSE OF SOUND IX OKGAN-PIPES. 



It is stated in the ordinary text-books that in the mouth- 

 piece of the so-called flute pipes of an organ the current of 

 air which causes them to sound breaks against the upper lip 

 into a series of intermittent impulses, by which the air in the 

 pipe is set into vibration. Gonuch, however, who is an or- 



