TKANSACTIONS OF SECTION A. 565 



or floating' was very decided; but in a few cases the observations needed a 

 considerable amount of care. For instance, solid lead would readily sink when 

 the temperature of tlie liqiiid was mucli above its melting point ; but just at its 

 melting point the sinkage was so very slight that there was some difficulty 

 in determining whether the solid really did sink or not, a thin film of dirt being 

 quite sufficient to keep it from sinking. With phosphor bronze, brass, and the 

 second white metal, the flotation of the solid was very slight ; but with the other 

 bodies of Class B the floating was very decided. Copper, a body usually given as 

 a sinking solid, floats with considerable buoyancy. 



14. On Drops and Gafillarity. By Dr. T. Woods. 



The intention of this paper is to show that every liquid has a specific volume of 

 drop, a definite number of drops of each liquid always occupying the same bulk 

 under similar circumstances ; and that, however varied circumstances may be, 

 provided they change equally with all, the relation of volume of drop is maintained 

 between the several liquids examined. 



In it is also shown that this specific volume is proportional to the capillarity of 

 the liquids — the greater the capillarity the larger the drop. 



It is suggested that this property may be useful in analysis — a ready method, 

 for instance, of detecting the amount of dilution of a fluid. 



1-5. On Binaural Audition. — Part III.' 

 By Professor SiLVANUS P. Thompson, B.A., D.Sc. 



The beats of mistimed consonances of the form n : 1 have lately claimed some 

 attention on account of the revival of the dispute between Dr. Konig and the 

 mathematical acousticians concerning the origin of the difierence-tones or grave 

 harmonics, Konig holding to Smith's theory that the beats, when sufficiently 

 rapid, pass into Ijeat-tones, which all mathematical physicists agree is physically 

 impossible if the tones are simple, and if so small an amplitude that the squares 

 and higher powers of the displacements may be neglected A very important paper 

 on this matter, by Mr. Bosanquet of Oxford, has lately appeared (' Phil. Mag.' 

 June 1881), in which he states: (i.) that these tones are subjective; (ii.) that they 

 consist of variations in intensity of tlie lower tone; (iii.) that if the squares and 

 higher powers of the displacements be not neglected in the equations, a term appears 

 having a period whose frequency is the diflerence of the frequencies of the 

 generating tones, as required by Helmholtz's theory of the difl'erence-tones. 



This question was alluded to in the author's previous papers on Phenomena of 

 Binaural Audition (' Brit. Ass. Eep.' 1877, 1878). He found beats to be heard, but 

 not differential tones, from two tones led separately to the two ears. 



The author has lately examined with care the beats of the mistimed unison, 

 octave, twelfth, and double-octave, bringing the sounds separately to the two ears 

 by tubes. He has heard beats in all these cases, and in every case found them to 

 consist of variations in intensity of the lower tone. The use of resonators 

 intensified the phenomena. 



The author also recounted experiments in which partial interference was 

 obtained between an objective tone, and a subjective tone imposed upon the ear by 

 fatigue. 



He also announced a new illusion of binaural hearing due to fatigue, the 

 apparent dii-ection of a source of sound being altered by the previous fatigue of 

 one ear. 



16. On Differential Resolvents. By the Rev. Robert Hakley, F.B.S. 



Printed in full, Phil. 3Iay., Nov. 1881. 



