1854.] 



ATMOSPHERICAL ELECTRICITY. 



157 



on the sanie subject at Broornfield for thirty years. Crosse's 

 atmospheric apparatus consists of wire, one third of a mile in 

 length, insulated upon poles or upon the tops of trees in his 

 park. By the slight motion of a lever, the electricity from the 

 air is introduced into his study or dismissed into a safety 

 channel which is connected with the ground. Crosse's wire is 

 higher above the level of the sea than Weekes's apparatus, but 

 it does not stand so high above the ground underneath, and 

 hence it did not manifest so energetic symptoms of electricity. 

 But even this sufficed to charge and discharge a Leyden battery 

 with seventy-three feet of coated surface, twenty times in a 

 minute, and with a report as loud as that of a cannon. Strangers 

 ran away, and an exaggerated report was spread, that the neigh- 

 borhood was filled all the time with thunder and lightning. 

 This alarm had the advantage of protecting the fruit-trees of 

 Crosse from the depredations of vagrants. Crosse is a retired 

 country gentleman, and has spent fifteen thousand dollars on 

 his apparatus, although he is his own mechanic. In spite of his 

 own modesty he has obtained celebrity from those experiments, 

 on which the author of the "Vestiges of Creation" has laid 

 stress. Sir Richard Philips has given some account of a visit 

 which he paid to Crosse's scientific establishment. He found 

 there his voltaic magazine, consisting of 2500 pairs of voltaic 

 elements, 2,000 of which were in operation at one time. 



The immense length of telegraph-wire standing in this country 

 and elsewhere has entirely eclipsed the apparatus of Weekes 

 and Crosse, though not originally intended, nor often used, for 

 studying atmospherical electricity. Even when the wire is not 

 struck, it is electrified by induction, and the lightning begins to 

 make the record on its own account. Sometimes this induced 

 action is felt at the distance of twenty miles. A storm at Bal- 

 timore has set the magnets in motion at Washington. Professor 

 Henry has recorded a case, where the writing part of the tele- 

 graph began to work at one end of the line, from the influence of 

 a snow-storm at the other end. The presence of induced elec- 

 tricity on these wires will also betray itself by a spark wherever 

 there is a break. 



I have finished the general description which I intended to 

 furnish of the various appliances to which observers have resorted, 

 in testing the presence, and character of atmospherical electricity. 

 And I am now ready to give some of the results of their inves- 

 tigations : such, at least, as have not been already anticipated. 

 The first and mo"st fundamental of these results was the discovery 

 of the reality of atmospherical electricity; the determination, that 

 is, of the identity between lightning and electricity. This iden- 

 tity, speculatively dreamed by Gilbert and revived in tire minds 

 of Hawksbee, Wall, Winkler, Gray, Nollet, was apprehended by 

 Franklin with a clearness and force of conviction which did not 

 let him rest until he had settled the question experimentally. 

 The proof of this identity consisted in drawing down the lightning 

 from the skies in moderate quantities, and performing with it 

 the common experiments of electricity. As the science of elec- 

 tricity has acquired a wider range by the discovery of voltaic 

 electricity and electro-magnetism, an opportunity has been 

 afforded for placing the identity of atmospheric and common 

 electricity upon a broader basis. While, therefore, Franklin and 

 his contemporaries charged the Leyden jar with lightning, and 

 showed the shock, the spark, the heat, of electricity, Sturgeon, 

 Colladon, and Peltier have used it to magnetize steel needles and 

 to deflect the galvanometer. 



Other results which have been experimentally obtained are in 

 answer to such questions as these: — Is the electricity of the at- 

 mosphere and of the clouds positive or negative? How is it 



distributed ? What relation does it bear to times and seasons ? 

 How is it produced ? What are its effects ? 



With regard to the character of the electricity, it may be said 

 that the earth is generally charged negatively, and the atmos- 

 phere positively ; the intensity of the positive charge increasing 

 with the elevation of the stratum observed. Any discrepances 

 between observei s in respect to this point may be referred to local 

 action. Peltier has proved the negative character of the solid 

 earth as compared with its atmosphere by means of the gal- 

 vanometer. One end of the multiplier was joined to a pointed 

 rod of metal and raised into the air, the other end being soldered 

 to a metallic plate which was buried in the earth. As the elec- 

 tricity under examination possesses considerable tension, the 

 the strands of the multiplier must be insulated from each other 

 with unusual care. Sturgeon found the electricity of the air 

 most positive during the cold northeast winds of March. Weekes 

 observed that the electricity was strong when there was a breeze 

 from the eastward. Cuthbertson states that he always found the 

 electricity of the air positive. Crosse, on the other hand. thought 

 the air was always negative. Davy, too, in his Agricultural 

 Chemistry, seems to imply that the air is negative. In some of 

 the observations, probably, the -requisite precautions were not 

 taken to guard against deception. Pine cautions the observer 

 against making his experiment near a tree. The free electricity 

 of the ah-, positive in character and increasing with the elevation 

 of the spot observed, is not found in the interior of buildings. 

 The air of rooms vitiated by respiration is negative according to 

 Murray. He also states that the air at Orbitello and in the 

 Pontine Marshes is negative. The most intense charge is ob- 

 served in open places, such as quays, bridges, and squares. In 

 such localities as Geneva, where low fogs prevail, it is particularly 

 intense. A persistent series of systematic observations in elec- 

 trical meteorology may perhaps bring these discordant and 

 anomalous results of observation into harmony with each other. 

 It is no small part of the difficulty, that the instruments which 

 report of the electrical state of the air may, like those which 

 measure its temperature, or its moisture, or its winds, respond 

 more promptly to local than to general influences, and so give an 

 uncertain^sound, instead of registering that state, as the barometer 

 registers the physical element to which it is adapted, in its most 

 general character. A series of daily observations made by 

 Schubler, at Stuttgard, from May, 1811, to June, 1812, in all 

 kinds of weather, may throw some light upon the subject. He 

 reached the following results: — 1. The charge of electricity is 

 more intense in storms of rain, or hail, or snow, than when the 

 sky is fair. 2. At such times the charge is as often negative as 

 positive. 3. The character in this respect often changes sud- 

 denly. 4. In cloudy weather, without any storm, the charge is 

 positive. 5. The intensity of the charge is greater in winter than in 

 summer. Schubler also studied the electrical phases of the atmos- 

 phere at different periods of the day, and discovered some corres- 

 pondence between the diurnal variation of the magnet and the 

 daily curve of electrical intensity. The minima of intensity oc- 

 curred before sunrise and again two or three hours after noon, 

 and the maxima two or three hours after sunrise and after sun- 

 set. The range of the daily change increased from July to 

 January, and decreased from January to July. In 1830, Arago 

 repeated at Paris the same series of observations on the daily 

 curve, and with similar results. 



As a body becomes positively charged only at the expense of 

 another which loses electricity and is therefore negatively charged, 

 the electricity of the air and of the clouds, whether in fact posi- 

 tive or negative, implies the existence of an opposite charge in 

 the earth itself. The solid earth, with its atmosphere, has the 



