L GENERAL SUMMARY OF SCIENTIFIC AND 



Deeharme has given a novel method of producing sono- 

 rous vibrations, lie simply blows a current of air through 

 a tube, the lower end of which is just even with the surface 

 of mercury contained in a suitable vessel. This yields a dis- 

 tinct sound, and at the same time the mercury is thrown 

 into circular waves, producing a symmetrical network on its 

 surface. The smaller the interior diameter of the tube, the 

 more acute and feeble the sound and the finer the waves. 

 He recommends, as the best, tubes between 0.8 and 5.0 milli- 

 meters in interior diameter, fixed vertically, and supplied by 

 a uniform current of air. By having a series of properly se- 

 lected tubes, the surface of the mercury may be made to as- 

 sume any sets of waves and interferences; and by illuminat- 

 ing them strongly, they may be projected on a screen as an 

 admirable lecture experiment. The same author has de- 

 scribed a new form of sonorous flame. When gas under the 

 ordinary pressure is burned from an opening three to five 

 millimeters in diameter, a flame thirty to fifty centimeters in 

 height is obtained. If now, by means of a similar tube held 

 horizontally, a moderate current of air be directed against 

 the flame, persistent and very varied sounds are produced. 

 The experiment succeeds very well with a Bunsen burner 

 giving a luminous flame (its air-openings being closed), the 

 tube supplying the air being placed horizontally a little 

 above the orifice and in contact with the flame. The phe- 

 nomenon acquires special interest when viewed in a revolv- 

 ing mirror. In a subsequent paper he gives experimental 

 reasons for believing that the air which is blown against the 

 flame, and which lie supposed to act solely mechanically, 

 plays also a chemical part. He finds that, using a Bunsen 

 burner, the sound is extremely feeble unless the air-openings 

 be closed and the flame be luminous. Moreover, neither car- 

 bon dioxide nor nitrogen gases will produce the sound unless 

 oxygen be mixed with it. The author hence believes that 

 the sound results from the small explosions which are inces- 

 santly produced by the combination of the oxygen of the air 

 with the carbon and hydrogen of the flame when the com- 

 bustion of this is already incomplete. That the sound should 

 be well-pronounced, therefore, the presence of air or of oxy- 

 gen mixed with some inert gas is necessary. 



Bresina has described a simple method of comparing the 



