PART iv. OCCASIONAL PHENOMENA. 49 



be set up also by terrestrial rotation, giving rise to an 

 electrical discharge from the outgoing equatorial stream 

 to the Polar regions, where the atmosphere to be pierced 

 by the return flood is of least resistance." 



In short, Dr. Siemens shows that the production of 

 an extra quantity of invisible watery vapour at any time, 

 on any one of the globes of the solar planetary system, 

 produces in time an effect upon them all through means 

 of the medium, exceedingly rare but still a gaseous 

 medium, in which they move and have their existence ; 

 and wherein the association at one time, and disassocia- 

 tion at another, of the gases forming watery vapour 

 through the many agencies of light, heat, electricity, 

 rarefaction, and condensation, is one of the most moving 

 importance to the preservation of all the life we know of, 

 and the maintenance of the present order of things 

 throughout the starry universe. While, once more to 

 quote Dr. Huggins, " Further, it is supposed that the 

 luminous jets, and streams, and caps, and envelopes 

 (of the head of a comet) belong to the same order of 

 phenomena as the aurora, the electrical brush, and 

 the stratified discharges of exhausted tubes." 



This last order of artificial phenomena is precisely 

 what the Madeiran cloud of June 26 reminded me of in 

 its general appearance, which is all that I can speak to. 

 So that, for more precise ideas of its nature, we can only 

 hope that the permanent island residents will themselves 

 prosecute the instrumental observation of their extraor- 



E 



