On the Properties of Electric Waves. 55 



It will be noticed that in the case of the third mixture of 

 the density and thermal expansion series (the same mixture) 

 the differences are comparatively large, but it is obvious 

 from the data of the fourth column in these series that the 

 ionization-coefficients have not been accurately determined 

 for mixtures of about the concentration of the one referred 

 to. With these exceptions the agreement between observed 

 and calculated values is satisfactory, the differences being 

 either well within or at worst on the limit of observational 

 error, up to mean concentrations of about 1*5. The determi- 

 nation of the ionization-coefficients was especially difficult in 

 the case of the surface-tension observations, because Rother 

 mixed equal weights of his simple solutions, not equal 

 volumes. Nevertheless, in all except the strongest of these 

 mixtures, the differences are probably not beyond the limits 

 of experimental error. Obviously, alternation of sign is not 

 to be expected in these calculations. 



[To be continued.] 



IX. On a complete Apparatus for the Study of the Properties 

 of Electric Waves. By Jagadis Chunder Bose, M.A. 

 (Cantab.), D.Sc. (Lond.), Professor of Physical Science, 

 Presidency College, Calcutta*. 



rpHE work of Hertz and his eminent successors, both heref 

 *~ and on the Continent, has opened out for study a new 

 region of asthereal vibration, bridging over the gap that 

 hitherto existed between the comparatively slow sether vibra- 

 tions and the quick oscillations which give rise to radiant 

 heat. In the vast range of possible aether vibrations we 

 recognize only a few octaves by our senses ; the rest are 

 beyond our perception. Many unexpected properties of 



* Read before the British Association at Liverpool, 21st Sept., 1896. 

 Communicated by Lord Kelvin, F.R.S. 



[Tbe apparatus described in this communication is founded on Prof. 

 Oliver Lodge's and M. Branly's discovery of the " coherer" for detecting- 

 electric waves. The general design of the apparatus, both in respect to 

 generator ar>d receiver, was given originally by Prof. Lodge, and described 

 in his book ' The Work of Hertz and some of his Successors, published 

 by the Electrician Co. in 1894. — Editors.] 



t By " here " is meant not only England, but Professor Lodge's 

 laboratory especially, where the paper was read, and where, as is well 

 known, some of the most important investigations on electric radiation 

 have been carried out. For my interest in the subject I owe greatly to 

 Prof. Lodge. 



