ya7i. 17, 1878] 



NATURE 



227 



are not resolvable, and particularly of those which assume 

 a spiral form. 



He describes an experiment in which a cloud of metallic 

 matter attracted to an electrode by the electric current 

 assumes in the centre of the liquid a gyratorj' spiral move- 

 ment under the influence of a magnet.' A glance at Figs. 



2, 3, and 4, which represent this experiment, is suffi- 

 cient to enable us to recognise their similarity to the 

 forms of spiral nebulae described by Lord Rosse. 

 Some of these have the curvature of their spirals tend- 

 ing in a direction opposite to that of the hands of a 

 watch, like those in Fig. 3, such as in the nebula 



Fig. I.— Arrangement of 400 couples in ten batteries for experiments with electric currents ot high tension. 



in Berenice's Hair ; others have their spirals in the same 

 direction as the hands of a watch, like that of Fig. 4, as 

 in the nebula in Canes Venatici. M. Plantd is inclined to 

 believe that, in presence of an analogy so striking, -we are 



authorised to think that the nucleus of these nebulae may- 

 be constituted by a true centre of electricity ; that their 

 spiral form may be determined by the near presence of 

 celestial bodies strongly magnetic, and that the direction 



r.u. :•. l',... 3. Fic. 4, 



Fio. 2. — Cloud of metallic oxide formed in a voltameter before the approach oi a magnet. Figs. 3 and 4.— Gyratory movement communicated to the cloud 



of metallic matter by the action of a magnet. 



of curvature of the spirals may depend on the nature I of the magnetic pole turned towards the nebula. He 



J It is easy to reproduce this e.vperiment and even throw ihe effect on a 

 screen, by means of an electric current equivalent to that of fifteen Bunsen 

 elements. The electrodes are copper wires : the liquid is acidulated with i-roth 

 of sulphuric acid. From the extremity of the positive wire escapes, with a slieht 

 hissing sound, a thick cloud of the protoxide of copper or of finely-divided 



copper, and this wire lakes the fonn of a very sharp point. The arrows 

 around the spirals in the figures indicate the gyratory movement which this 

 cloud assumes under the influence of a magnet : and the arrows around the 

 magnet represent the direction of the electro-magnetic currents ; b is the 

 north and a the south pole. 



