494 



SCIENCE 



[N. S. Vol. L. No. 1300 



is practically identical with tlie upper wave 

 limit, that is, the boundary reached by the 

 waves during storms. This limit is marked 

 roughly by the line of driftwood and the 

 lower limit of vegetation. The singing sands 

 are therefore all subjected to periodical con- 

 tact with the water of the lake and are moist- 

 ened and washed by that water. 



These observations include, I think, all the 

 obvious ones in connection with the singing 

 sands. The most casual observer will remark 

 with astonishment their very sharply defined 

 upper limit. As one walks from the water's 

 edge up the beach and crosses the upper wave 

 limit, he notices a sudden cessation of sound 

 as he passes the upper line of driftwood and 

 the commencement of vegetation. Beyond 

 this point he may proceed into a blowout of 

 clear sand quite identical in appearance, 

 macroscopic as well as microscopic, and of 

 the same composition by ordinary methods 

 of analysis and yet this sand fails entirely 

 to produce the sound of the beach sand. His 

 first conclusion would be that the proximity 

 of the water and waves of the lake must have 

 some relationship to the sound-producing 

 grains. 



I wish to apologize in advance for offering 

 an hypothesis of this sound production un- 

 supported by convincing evidence. What fol- 

 lows may, however, serve as a working basis 

 for other investigators and may lead to a true 

 explanation of the sound-production. 



My hypothesis briefly stated is this. The 

 sand grains on the lower beach and as far as 

 the upper limit of the storm beach are bathed 

 periodically by the waters of the lake which 

 contain various salts including calcium and 

 magnesiinn bicarbonates. This water dries on 

 the grains of sand, coating the surfaces with 

 an extremely thin film of salts including cal- 

 cium and magnesimn carbonates. This film 

 is of such a nature as to create considerable 

 friction when rubbed and thus when the 

 grains are brought into contact with various 

 surfaces a sound is emitted. One may com- 

 pare the action of the film of dried salts on 

 the sand grains with the action of rosin on 

 the violin bow. The beach sand is, of course, 

 the same sand which later goes to form the 



dunes when transported by the wind but dur- 

 ing this transportation, due to the abrasive 

 action of grain against grain, much of the 

 salt film is rubbed off and carried on by the 

 wind in the same manner that clay dust is, 

 to be deposited in quiet places as on the forest 

 floor beyond. After deposition in blowouts or 

 on dunes, the grains are subjected from time 

 to time to the leaching action of rain water 

 and this completes the removal of calcium and 

 magnesium carbonates (in the form of bicar- 

 bonates and of the other salts) so that the 

 original sand grain surface is restored or, 

 to speak metaphorically, the sands lose their 

 singing voice. Such is the hypothesis. 



A typical analysis of Lake Michigan water 

 shows the following constituents :^ 



Parts per 

 1,000,000 



Total residue 144.8 



Loss on ignition 17.6 



Chlorine 4.2 



Sodium Na 8.3 



Ammouium (NHj) .05 



Magnesium Mg 10.9 



Calcium Oa 28.2 



Silica Si 1.9 



Nitrate NOs 1.0 



Chloride CI 4.2 



Sulphate SO, 10.0 



Some samples of Lake Michigan water 

 show a higher content of solids than that 

 given in the above analysis, the maximum be- 

 ing about 160 parts per million. 



Wlien the singing sand from the beach is 

 compared with dune sand or blowout sand 

 under the microscope no difference is per- 

 ceptible. When subjected to screen tests, the 

 beach sands show themselves to be of the same 

 physical composition and texture. By chem- 

 ical analysis, according to the usual methods 

 of conducting mineral analyses, both show the 

 same composition. The amount, therefore, of 

 salts in the hypothetical film above referred 

 to must be therefore within the limits of an- 

 alytical error. 



Experiments to prove or disprove the hy- 

 pothesis readily suggest themselves. Some of 



2 Bull. No. 10, Illinois State Geological Survey, 

 1909, "The Mineral Content of Illinois Waters." 



