750 Mr. njiarU^ E- ^- Phillipf^ [Feb. 11, 



filled. On freeing the nozzle you see that the sand moves out by 

 slow regular jerks. Certain curious rattling sounds, emitted occasion- 

 ally by the column descending in a glass tube, also drew attention to 

 the intermittent motion of the grains. 



It seemed reasonable to hope therefore that this might be made 

 sufficiently rapid and regular to give rise to a musical note. 



Now many strange noises have been heard in the neighbourhood 

 of large sand masses, when surface layers have been disturbed by 

 someone walking over them. And there are curious shrieking sands 

 — rarely met with upon the coast. 



Thanks to the great kindness of Mr. Carus-Wilson, whose work 

 in this direction is so well known, I am able to exhibit a remarkable 

 specimen of sand from the Isle of Eigg in the Hebrides. When a 

 plunger strikes down upon the grains contained in a suitable cup, 

 you hear a piercing musical sound. Mr. Carus-Wilson attributes 

 this to the friction between the particles, the effect being produced 

 in much the same manner as that which results from gently rubbing 

 an agate style upon glass. He has discovered musical sand in Poole 

 Harbour as well as at other places. 



The essential conditions for the production of this sound are : — 



1. That the grains be nearly of the same size and rounded. 



2. That they be clean and free from adherent fine dust. 



\ 3. That the vessel in which they are struck have sloping sides 

 and be made of a suitable material. 



But to return to the question of obtaining musical sounds from 

 ordinary sand. 



There stands, fixed to the wall, a large glass-fronted section of a 

 tube. It is filled with alternate bands of white and black sand, the 

 latter l:>eing about one-sixth as deep as the former. An outlet is 

 provided at the bottom. This arrangement enables the motion of 

 the different portions of the sand column to be observed while the 

 powder issues from the orifice. 



On freeing the nozzle we see that the centre of the lowest 

 black band immediately falls, and that as the sand continues to 

 escape, successive l)ands become similarly deformed. It is clear that 

 the grains from the central part of the column are moving rapidly 

 downward, and since no eddies can form in the remainder, the whole 

 becomes divided into a core of moving particles and a large sur- 

 rounding mass of dead sand. (Fig. 11.) 



The "diminished density of the axial region releases the lateral 

 pressure upon the sides of the tube, and the upper part of the column 

 suddenly slips until the grains again pack and seize as before. 



Now if sand of a suitable fineness be slowly passed in this manner 

 through a glass tube of correct dimensions, a musical note may be 

 produced. 



The tube should be about 1 inch in diameter, and filled with sand 



