xxxiv SCIENCE PROGRESS. 



this arrangement has not been used in connection with a series of reso- 

 nators to estimate the intensity of the overtones of notes produced by 

 various instruments. The author in this section also gives an account 

 of A. Konig's explanation of the transverse ridges in which cork filings 

 in a Kundt's tube set themselves. The explanation depends on the fact 

 that two spheres at a moderate distance apart in an alternating current 

 will, on account of the difference in the velocity of the air between them 

 and that along their averted hemispheres, repel one another if the line 

 joining the centres is parallel to the direction of motion of the air, and 

 will attract one another if the line joining the centres is perpendicular to 

 the stream of air. The result of these forces being a tendency to ag- 

 gregate in transverse lamina. 



In the chapter dealing with the vibration of organ pipes the author, 

 while mentioning the observations made by Topler and Boltzmann, in 

 which the optical interference between two rays of light, one passing at 

 the side of the pipe and the other through the air in the pipe, which, on 

 account of the vibrations, is alternately compressed and rarified, does 

 not mention the beautiful results obtained by this method by Raps 

 (Wied. Ann., 50, 193, 1893). 



The subject of singing flames and such like, in which the vibra- 

 tions are maintained by heat, is a most fascinating one. The complete 

 explanation of the phenomena on account of the peculiar and ill-under- 

 stood behaviour of the flames being a matter of considerable difficulty. 

 The author discusses Sondhauss's experiments in this subject, and 

 shows how the eftects may be explained on the supposition that sta- 

 tionary vibrations are set up in the gas supply tube, the phase of which 

 may be either the same or opposite to that of the vibrations in the 

 resonator. Since it is probable that the greatest development of heat 

 is slightly retarded in comparison with the issue of gas, there will be 

 a tendency, according to the difference in phase, either to maintain or 

 to damp out any existing vibrations in the resonator. The vibrations 

 set up in glass bulbs when heated, a phenomenon familiar to all glass- 

 blowers, is another example of vibrations maintained by heat, and in 

 this connection the author might have considered the very interesting 

 thermal engine exhibited, we believe for the first time, by Mr. Griffiths 

 at the meeting of the Physical Society held in the Cavendish Laboratory 

 a year or two ago. It consists of a glass bulb about 6 cm. in diameter 

 connected to a U-shaped tube ot about i cm. bore. The U is filled 

 with mercury for about 6 cm. up each limb and the bulb heated over a 

 flame. If the mercury is disturbed by plunging a rod into the open 

 limb of the U, oscillations are set up which increase in amplitude to a 

 most astonishing extent, and are maintained as long as the heating 

 continues. 



The additional chapters, to which we have not space to refer in 

 detail, deal with the eftects of friction and heat conduction on acoustical 

 problems, capillarity and capillary waves and ripples, vortex motion 

 and sensitive jets, vibrations of solid bodies, and finally a long chapter 



