184 



ATMOSPHERICAL ELECTRICITY. 



[1854. 



■which treats of it, beyond the region of twilight to a spot as 

 distant as any of which gives indications of the existence in it of 

 any substance affiliated with the grosser matter of the earth. 

 Now the relation which has been observed to hold between the 

 direction of the dipping needle at any place and the vanishing 

 point of the auroral beams, indicates a dependence of the 

 aurora on terrestrial magnetism, that is, upon an inseparable 

 property of the earth. Again, it is supposed the clouds do not 

 shine entirely by the light of the sun, but that they are them- 

 selves to a small degree self-luminous. In proof of this, Mr. 

 Spencer alleges the case of an astronomer who could not see to 

 read his time by bright starlight, but was able to do it after the 

 heavens were overcast with clouds. Now it has been suggested 

 that these instances of phosphorescence in clouds are the effects 

 and the tokens of their electricity. The meteoric wonders of 

 luminous rain and snow may indicate a high charge of elec- 

 tricity in the air breaking out into a glow. In other cases, as 

 for example, in the moon, the planets, and the comets, where 

 it is known that the bodies shine eminently by reflected light, 

 that small amount of independent light which they may emit 

 from a sort of phosphorescence is liable to be overlooked and 

 over-drenched in the superior brilliancy of other lights; but 

 these independent rays, where they exist, may be the nice 

 traces of electricity. 



There are motions among the clouds which are probably caused 

 by the electrical attractions and repulsions. It is no uncommon 

 sight to behold clouds moving contrary to the wind, and also 

 sometimes in different directions with respect to one another. 

 This is properly explained, in many cases, by saying that different 

 currents prevail at different heights, and each cloud obeys, like 

 a balloon, the current in which it happens to be at the time. 

 But it is impossible that the clouds should be electrified, as they 

 sometimes are to a high degree, without exerting their electri- 

 cal attractions and repulsions, and thus producing motions which 

 may modify, and perhaps materially, such other motions as the 

 winds may start On the 14th of June, 1842, it was observed 

 that the focus of a thunder-storm in England followed the course 

 of the Thames. There, the electrical forces seemed to im- 

 press their own character upon the direction of the motion. 

 The clouds acted by induction upon the earth, and, particularly 

 on those parts which conduct the electricity best, and pre- 

 pared the way for the attraction which guided their own 

 course. 



Another way in which electricity may influence the atmos- 

 pherical movement is this. When the particles of air are electrified, 

 they tend to fly asunder, as the pith-balls hanging upon the 

 prime conductor of the electrical machine. This tendency of 

 the particles to separate adds to the expansive force of the air, 

 and is equivalent to so much additional heat. A large amount 

 of electricity set free at one place may give a strong explosive 

 force to the air, and produce in this way very grand effects, 

 though they will be local and ephemeral in their character. But 

 in a general view of meteorology this mode of action cannot be 

 paramount to all others. For when it is considered that heat 

 acting by one or another agency, produces the electricity 

 which is in the air, it can hardly be believed that a given 

 amount of heat if exerted directly on the air to expand it. 



Faraday once made a remark, based upon his own experiments, 

 which is often quoted and sometimes misconceived, to this effect: 

 that a grain of water gives out by its chemical decomposition as 

 much electricity as might charge a thunder-cloud. Hence 

 many exclaim, philosphers and those who are not, How immense 

 the quantity of electricity in a drop water! We might with as 

 good reason cry out, How insignificant the quantity of elec- 



tricity in the thunder-cloud ! And, indeed, if electricity he in 

 reality "a fluid, as we at present are constrained to conceive it, the 

 grand effects which are unquestionably produced by it, as those of 

 the thunderbolt, may be attributable to the incomparable free- 

 dom, elasticity, and consequently the velocity of the fluid, and not 

 the quantity, which may be no greater than that which binds the 

 oxygen and hydrogen of a particle of water, and which if gradu- 

 ally set free, is insignificant and almost imperceptible. There 

 may be other local effects besides these seen where lightning 

 has struck, as for example, the ravages of the tornado, which are 

 the work of electricity suddenly accumulated and bursting 

 as suddenly out before it has had time quietly to discharge 

 itself by the ordinary channels. In the convulsions of the air, 

 and even of the solid earth, in earthquakes, volcanic eruptions, 

 and hurricanes, electricity finds a congenial atmosphere and 

 contributes to swell the force of destruction. But even here, 

 while its makes it own mark on the phenomena, it is itself the 

 effect of man} r antecedents, and can be no larger or more terrific 

 than the forces which have been expended in producing it. 

 These other forces, it is true, by taking the guise of electricity, may 

 acquire a degree of centralization and a facility for instan- 

 taneous action which do not belong to their own sluggish 

 nature. 



Thus, in various ways, such as have been already described, 

 electricity is ascending from the earth to the air, or in other 

 words, the electrical equilibrium holding between the earth and 

 its atmosphere is destroyed. Even while the accumulation is 

 proceeding, some effects, as the electrical attraction and rejjulsion, 

 and the motions which follow, are produced by these forces, 

 the release of which from the usual balance is the essence of 

 electricity. But in the course of time the clouds will be electri- 

 cally overloaded, and the forces of which I write will be so 

 strengthened by constant reinforcement as to compel a return 

 to equilibrium. The influences which carry up the electricity 

 into the air cannot hold it there. This must be left for the 

 insulating power of the air itself, which is generally very imper- 

 fect. In dry states of the air, the electricity must wait till it is 

 strong enough to break down in luminous beams through the 

 dry air, revealing its motion possibly at these times by the 

 tremulous flashes of the aurora. Sometimes its passage from 

 cloud to cloud is bridged across by the moisture, or its descent 

 to the earth is made very easy by the columns of rainbows or 

 snow-flakes. But whether it creeps slyly from place to place or 

 dashes boldly along, as in the lightning, the most important dis- 

 turbances are produced by the electricity of the atmosphere, as 

 well as electricity in general when it is in motion, when it is 

 hurrying back to the haunts from which it was enticed. Then 

 it burns, blazes, storms, and tears, then it convulses and some- 

 times kills. Manifest pains has been taken by the Author of 

 nature to keep down all electrical excesses. The lightning 

 which kills suggests most forcibly the Merciful Hand which 

 generally spares. Even if we are not able to decide whether 

 the development of electricity is incidental merely to other at- 

 mospheric movements, or whether it is a most important ob- 

 ject of them, certain it is that electricity is crowding into the 

 air, and in quantities that would threaten all the time, did not In- 

 finite Wisdom provide in more ways than one an escape for 

 the redundant energy, and ages before Franklin planted on the 

 earth the first lightning-rod to catch the destructive fluid as it 

 poured down, make the earth bristle all over with his divine 

 protection. The method by which the earth is shielded from 

 the electrical furies, the cases in which the defence is insuffi- 

 cient, the ways by which man has guarranteed to himself 

 greater security, and the effects of lightning when, in spite of 



