386 



NA TURE 



[March 14, 1878 



proceeds from the reaction due to the flowing of the elec- 

 tric flux. As to the rings, they are formed in a visible 

 manner, under the eye of the observer, by the more and 

 more rapid movement of the blue points, and by the per- 

 sistence of the impression upon the retina,. 



When the metallic electrode is positive and the dis- 

 tilled water negative, the spark still assumes externally an 

 ovoid form ; but the middle is traversed by a cone of 

 violet light. When we employ two metallic electrodes 

 we obtain a luminous spheroid, the interior of which is 



traversed by a brilliant line. This appearance corresponds 

 to the spark, and the aureole of the spark seen in the 

 discharges of an induction coil ; only here the aureole 

 occupies more space, in consequence still of the greater 

 quantity of electricity. In fact, if we much increase the 

 length of the column of water interposed, we do not obtain 

 more than an arc or a straight line, 



M. Plants therefore thinks globular lightning may result 

 from an abundant flow of electricity in the dynamic state, 

 in which quantity is joined to tension. The particular 



Fig. 12. — Globular spark produced over distilled 

 water by an electric current of high tension. 



Figs. 13 10 17. — Cvoid sp^ks „nd luminous figures produced over distilled water by an electric 



curreni of high tensioa. 



case where globes of lightning present slow movements or 

 times of stoppage, is explained by the movement or the 

 repose of the column of moist air strongly electrified and 

 invisible, which serves as electrode. To imitate this effect 

 it is sufficient, in one of th© preceding experiments, to 

 make the electrode oscillate, it being previously suspended 

 under the form of a long pendulum above a basin full of 

 water or a metallic surface, and to mask by a screen its 

 lower extremity. We then see a little ball of fire move 

 above the water or the conducting surface, and thus 

 reproduce all the appearances of the natural phenomenon. 



surrounds the bottom of the stream takes a gyratory 

 movement in the opposite direction to that of the hands of 

 a watch if the pole of the electro-magnet is north, and in 

 the same direction as the hands if this pole is south. 

 The movement is rendered visible by light bodies spread 

 over the surface of the water. If we contract the stream so 

 as to avoid all solution of continuity at its lower part, the 

 electric and luminous signs disappear almost entirely. Thf» 

 liquid is, nevertheless, heated, as is shown byalight vapour, 

 and the gyratory movement is yet more pronounced and 

 rapid. On extending the stream anew the electric mani- 

 festations re-appear as before. 



This experiment reproduces the principal effects of 

 waterspouts, the rustling which proceeds from them, the 



I'lG. 18. — Experiment reproducing the efTdCt of waterspouts. 



Waterspotits — Cause a narrow stream of salt-water to 

 flow from a funnel provided with a cock communi- 

 cating with the positive pole of a battery of 400 secondary 

 couples ; the liquid is received in a basin containing the 

 negative wire and below which is an electro-magnet (Fig. 18). 

 As soon as the voltaic circuit is closed the stream appears 

 furrowed with bright lines at its upper part and traversed 

 by a luminous thread at its lower part. Sparks, illu- 

 minated aqueous globules, play with a rustling noise at its 

 extremity, vapour is disengaged, and the liquid which 



Fig. 19. — Electric bore. 



mist which is formed around them, the flashes of light 

 which furrow them, the globes of fire which sometimes 

 appear at their extremities — in such a way that, according 

 to M. Plants, these meteors may be compared to elec- 

 trodes of liquid or of vapour, from which escape to the 

 earth or the sea the powerful electric currents of storm- 

 clouds ; and if no thunder follows it is because the con- 

 ductor accompanies them to the ground, and there is in 

 this case no proper electric discharge, no more than 

 under the preceding conditions. 



The very formation of waterspouts, or the descent 01 

 these cloudy appendages towards the ground, has been 

 connected by Brisson and Peltier with an electrostatic 

 attraction between the clouds and the earth. We may add 

 to this very natural attractive force an action of transport, 



