CONDUCTORS, ETC.] UNDULATORY FORCES. ELECTRICITY. 



183 



ATMOSPHERIC ELECTRICITY LIGHTNING 

 CONDUCTORS THE ELECTRIC KITE, ETC. 



THERE are; perhaps, none of our readers who are not 

 familiar with the destructive resxilts which are occa- 

 sioned by severe thunder-storms ; and we shall now enter 

 into some examination of the phenomena of atmospheric 

 electricity, and explain the inventions of various kinds 

 which have been brought out for the purpose of averting 

 the danger arising from an over-accumulation of elec- 

 tricity in the air. 



Franklin was the first to discover that atmospheric 

 and frictional electricity are identical in all respects. He 

 was also the first " to draw fire from the clouds ;" except 

 we give that honour to Prometheus, whom some have 

 considered to have been the earliest inventor of lightuing 

 conductors. Franklin, for the purpose of ascertaining 

 the presence of electricity in the air, raised a small kite ; 

 having chosen, for that purpose, a day when a thunder- 

 storm was expected. For some little time no success 

 attended his experiment ; but when the string became 

 wet, and so was a better conductor, he was enabled to 

 draw sparks from it by means of a key, and so solved at 

 once the problems of atmospheric electrical disturbances. 

 Perhaps some of our readers may be desirous of re- 

 peating Franklin's experiment ; and it will, therefore, be 

 as well for us to give a little advice on the subject, and 

 BO to diminish the chance of danger which always arises 

 in such attempts. 



A kite, from four to six feet long, may be employed ; 

 and, at the top, a sharp metal wire should project about 

 two inches. This wire is to be connected with the long 

 :.? bv which the kite is to be flown. This string 

 should have a fine copper wire twisted inside the ex- 

 ternal hemp, which is easily done ; and, of course, 

 highly improves its conducting power. 



Great care is to be observed in flying the kite. After 

 raisin? it a short distance, a dry silk handkerchief 

 should be slipped round the string, noose-fashion, and 

 the extreme end of the string may be fastened round a 

 tree. The kite is raised by holding the string by means 

 of the silk handker- fig. 31. 



chief, so that the for- 

 mer may readily pass 

 through it. Of course, 

 the object of the silk 

 is to act as a non-con- 

 ductor, and so to pre- 

 vent the passage of the 

 electricity to the body 

 of the person hold ins; 

 it. The elevation of the 

 kite may be from 200 

 to 1,000 feet. The por- 

 tion of the cord wound 

 round the tree may 

 be loosed when the 

 kite is sufficiently ele- 

 vated, and its end is 

 to be attached to the 

 silk handkerchief, and 

 it will be ready for ex- 

 perimenting with. It is well to have the rod on which 

 the string is wound made of copper, with a ring at each 

 end. By means of this ring and the silk handkerchief, 

 the string may be fastened to a well-dried stick thrust into 

 the ground, as shown in the above figure ; and so the 

 conducting link will be broken with the earth, and sparks 

 may be obtained from the metal rod. In Fig. 32, a is 

 the metallic string proceeding from the kite, and 

 fastened on the ring b c is the metal rod ; d is the ring 

 to which the silk handkerchief, e, is attached ; / is the 

 ting of a post of dried wood, fixed in the ground ; q 

 is a discharger, the glass handle of which should be at 

 leant two feet long ; and h is a wire conducting the 

 electricity from d to the ground. 



The kite experiment should never be tried during 

 stormy or hazy weather, because such would most likely 



prove highly dangerous. Fatal accidents, indeed, have 

 occurred from want of caxition ; and we should not have 

 given directions for carrying out the trial, except under 

 the idea that some of our readers might resolve to 

 attempt it for themselves, and, in the absence of proper 

 precautions, might have sustained injury. We have 

 frequently adopted the plan we have described, and 

 therefore recommend it with confidence. It is, how- 

 ever, advisable that no tyro should ever attempt to fly 

 the kite under any circumstances. 



The most celebrated electrical experiments of this 

 kind, of modern times, are those which were conducted 

 by Mr. Crosse, of Bromfield, near Taunton, who was a 

 complete devotee to electrical science. This gentleman 

 erected, on ground near his house, a large number of 

 metallic rods, which were insulated at their lower end, 

 and joined together by a rod, the terminal of which 

 entered a room specially arranged for electrical experi- 

 ments. Opposite to the terminal was placed a rod of 

 metal, which, by sliding to and fro, could be fixed at 

 any required distance from the rod communicating with 

 the external conductors. By these means he was able 

 to conduct a thunder-storm and its effects into a small 

 space, and the results he obtained were of the most 

 extraordinary character. During stormy or hazy wea- 

 ther, brilliant flashes of light were observed between the 

 conductors, accompanied with terrific crashes of sound, 

 and violent reports. The entire effects were sometimes 

 quite appalling, and cannot be conceived by any one 

 who has not seen them. 



Now, it is plain, from these experiments and results, 

 that, by means of proper arrangements, electricity may 

 be conducted (to use an ordinary phrase) from the 

 clouds. But we must now be more philosophical in our 

 r.-marks, and explain the phenomena of thunder-storms, 

 (fee. , in accordance with the principles already laid down. 

 In doing this, we shall materially assist the student in 

 understanding the circumstances which attend the de- 

 velopment of atmospheric electricity, by comparing the 

 arrangement of the Leyden jar, or piece of flat-coated 

 pUt, with that of the clouds, air, and earth. We shall 

 consider, therefore, that the air corresponds to the glass 

 of the jar, the clouds to its inside, and the earth to its 

 outside coating. Lightning rig. 33. No. 1. 



conductors we shall nold in a 



the light of a discharger, ~". >h 



such as is usually employed No _ ?> 



in our experiments. This 

 may be better understood 

 by tho illustration which 

 the annexed engraving af- 

 fords. 



In Fig. 33, No. 1, we 

 have a piece of window- 

 glass, 6, coated at a and e 

 with tinfoiL Now, we have 

 already shown, that if a or 

 c be positively charged, the 

 opposite will become nega- 

 tively so by induction. Similarly, in No. 2, we shall 

 suppose the clouds, a, to be charged positively ; the 

 air, 6, which corresponds to the glass, ft, in No. 1, to be 

 intermediate between the clouds and the earth ; and the 

 earth, e, by induction, will necessarily be in a negative 

 state. 



In a former page,* we have stated, that when a jar is 

 overcharged, it will generally discharge itself ; and this 

 is exactly what occurs in nature. The high charge of 

 the clouds is spontaneously discharged to the earth ; and 

 just as we have the spark and snap of the jar, so, in the 

 large scale in nature, we have the flash of lightning and 

 the clap of thunder. It will thus be seen that the ana- 

 logv is complete. 



We may, however, go a step further, and remind oui 

 readers, that if a wire be stretched from n to c (No. 1) 

 whilst the former ia charged, the discharge takes place 

 without any external manifestation. In the very same 

 way if a tall metallic rod be raised from the ground, c, 



See ar.te, p. 179. 



