

1893.] Presents. 25 



due to the form taken by the bubble. The figures on the diagram 

 roughly represent the appearance of the bubble corresponding to the 

 different points where they are placed. The small bubble on the left 

 passes up rapidly. As larger volumes of air are taken to form the 

 bubble the velocity falls to a minimum, at which point the bubble is 

 almost spherical in shape. With further additions of air, the 

 spherical form gives way to one pointed at top. Again more air 

 swells out the top and gives the bubble a somewhat dumb-bell 

 appearance. For this and the spherical form the velocity is a 

 minimum. In these instances the ratio of the resistance of the 

 annular channel to the flow-past of the liquid compared to the 

 driving pressure is a maximum. The intermediate shape being 

 pointed at top gains an increased pressure head without a corre- 

 sponding increase in resistance. The various forms assumed by the 

 bubbles remind one of the well-known initial shapes taken on the 

 formation of liquid drops. 



Similar curves were obtained with other sized ' tubes, the phe- 

 nomenon being rather more marked in the case of the smaller sizes. 

 Other liquids were found to behave in a like way when used either 

 as the substance of the column or for constituting the bubble itself. 



The curve in the diagram exhibits the general behaviour of the 

 bubbles, but occasionally an anomalous determination of velocity will 

 be obtained ; this is accompanied by the bubble having also an 

 anomalous form. That is to say, a volume of air a little in excess of 

 that corresponding to the spherical stage, instead of assuming a 

 pointed form at top, will retain a spherical form, and as a consequence 

 will travel very slowly. 



V. On the Metallurgy of Lead." By J. B. HANNAY, F.R.S.E., 

 F.I.C. Communicated by Sir G. G. STOKES, F.R.S. Re- 

 ceived April 15, 1893. 



[Publication deferred.] 



Presents, June 1, 1893. 

 Transactions. 



Boston : American Academy of Arts and Sciences. Proceedings. 



Yol. XIX. 8vo. Boston 1893. The Academy. 



Briinn : Naturforschender Yerein. Bericht der Meteorologischen 



Commission. No. 10. 8vo. Briinn 1892. The Society. 



Essex Field Club : The Essex Naturalist. Yol. VII. Nos. 13. 



8vo. BuMurst Hill 1893. The Club. 



