'.ICES. ELECTRICITY. 



OUNDCCTOM. 



toward* tli. ol a iiilout i. 



takes pUoo; aiul this is proci*uly tho way in -.-, 



i act. The common 



ning conductor* uttroet tin- lightning an idi a . 

 entirely cn-oiioou*. ly form the roadie - 



uiont effectual mean >< electric o<{uilil>rimii 



ie earth a: ciul only to far arc they of any 



r purpose. 



\\ in iv l'ii. My glance nt some practical matters in 



'i witli this subject, which may be useful to 



,f our reader* desirous of putting our remarks into 



nduetr should have its upper end poiir 

 reasons previously explained.* Its lower end should IKJ 

 lea* than from three to four { ' :iii'>. dd--.l in tin- 

 earth, for tho same reason that we connect t 



I'.itu-ry with a gas or water-pipe, t Copper, b. 



r conductor than iron, is to be preferred; but gal- 



1 iron aiiswi-r-s vrrv well. 



All tho adjacent metallic objects, such as the leaden or 

 zinc roof of a house, should be connected with the con- 

 < -cause they might possibly act in independence 

 of it, and produce antagonistic results. The top of the 

 rod should extend much In-yond the highest part of the 

 building, aud should not be attached to the chimneys of 

 private houses, because the fine soot they contain is, to 

 some extent, a conductor. 



In many large buildings, such as churches, tin; stones 

 of the steeple, etc., are tied together by means of iron 

 clamps. In the absence of a conductor, these produce 

 the most serious results in a storm. The weathercock is 

 first struck as the most prominent metallic object, and 

 then every metallic tie in the building succeeds as a 

 ductor. These being at a distance from each other, do 

 not permit of a continuity of conduction ; and the result 

 generally is, that large stones are thrown down, and (lie 

 edifice often destroyed. Under such circumstances, the 

 building often is set on fire; and here we have an exact 

 analogy to the experiment of igniting gunpowder. We 

 stated in a previous page,; that tho pond.-r would be dis- 

 .1 if the wire were continuous, but would lie ignited 

 if a bad conductor, such as a wet string, were interposed. 

 This is just the case with the stones of the building. 

 Their non-conducting character prevents the rapi i 

 storatiou of the electric equilibrium; and hence the evo- 

 lution of heat and light. 



Occasionally, comparatively bad conductors arc struck 

 by lightning, and then destruction is sure to follow. 

 One of the most remarkable instances of this kind which 

 we have met with, was that of a flag-staff, forty feet 

 higli. * tho roof of a large inn opposite to the 



1'iison. Ilolloway ; the destruction of which occurred 

 during the early part of the summer of 1861. The staff 

 was rent to pieces ; but the course of the lightning was 

 in a screw form, from tho top to tho bottom of the wood, 

 every portion of which was divided into the t 

 splinters, so that it was impossible to touch any piece of 

 it except with injury to the hand. This . arise 



from the sudden expansion of the moisture in the t 

 of the wood, winch was good pine. When viewed by the 

 microscope, it appeared like a bundle of fine hemp I 



tig. 31. rather than solid wood. At 



lime of the occurren< 

 entire house seemed filled with 

 (lame, but no further damage 

 i-,' snlphu- 



mell was noticed for some 

 time afterwards. 



An experimental illustration 

 of tho effect of non-conduc- 

 -T of breaks in tho conduc- 

 tor, may be made by tho ar- 

 rangement represented in tho 

 annexed engraving. 



In tho rut, tho same ! I 

 are used for each figure, a is 

 No. S. a brtuw knob for re.-.-iviug tho 

 charge from a jar; 6 is a piece of dried wood, in the 



tec ante, p. 1:8. t Ante, p. 179. t .<'', P- 1*1- 



>a 



\ 



No. 1. 



J shape of the gable of a house ; e ia a win- conducting to 

 the earth ; and d is a small square of wo. -d. with tinfoil 

 p.vitcd on it, and movable in the l.f ST< , in 



No. 1, thfc liu-tor is continuous ! ,nd so tho 



.if ,!. i/, would not IK; disturb. 

 lint if a jar bo discharged on No. -. then tho wo. 

 will IKJ rapidly cjeetc.l from its place, because tin 



me course is broken by its position and that of tho 

 tinfoil being changed. 



Trees being moderately good conductors, are often 

 similarly injured ; but unless they are very dry, they 

 are not, gem-rally speaking, cloven into pieces. 



ial)y falls in a thunder storm, improves 

 the conducting power, and so renders them exceed- 

 ingly dangerous as places of shelter for man or ani- 



A singular circumstance came under our 

 t ice, three years ago, at < : sons had 



taken shelter under a tree, - subsequently struck 



with lightning. They wore all 



insensible for a time, from which they s-ooii recovered; 

 but, singular to say, the heels of their boots were com- 

 ly torn off, owing to tho conducting power of the 

 nails in them. This is another illustration of the re- 

 marks wo have just made, in reference to tho neccs.-. 

 continuous conductors from the different metallic 

 rangements in buildings. 



It seems a tolerably well ascertained fact, that persons 

 struck by lightning fatally, undergo rapid decomposi 

 The cause of this is by no means evident : it is stated, 

 however, in such instances, that the albumen of the blood 

 does not coagulate, as is usual in ordinary cases of death. 



When injury by lightning has taken place, it is well to 

 treat the person in the same manner as would bo adopted 

 for drowning; the object being to restore, as speedily as 

 possible , suspended animation. The latter is caused by 

 a cessation of the action of the heart, and consequent 

 asphyxia. Occasionally the application of electricity may 

 bo tried when the means of doing so are within reach ; 

 and, on breathing and feeling being restored, recourse 

 should at once be had to the warm bath, and subsequent 

 rubbing with very coarse towels. 



Before quitting tho subject of thunder-storms, we may 

 make a few observations on the cause of the rolling sound 

 of thunder. Tliis is entirely owing to tho echo produced 

 by the clouds overhead. The noise of the discharge 

 would, like that of tho Loyden jar, be single were it 

 i'ot for this cause. On a cloudy day, if the rejxirt pro- 

 duced by the discharge of cannon bo noticed, a precisely 

 similar effect is produced, and successive, instead of 

 single soui} ird. 



Another atmospheric phenomenon, most commonly 

 observed in the northern regions, is the aurora borealis, 

 the cause of which wo ascribo to a discharge of eh 

 city in a highly rarefied medium. \Vo have already 

 given an experiment illustrating its appearance in a 

 previous pago, and shall not further enter into the 

 subject here, as it more properly belongs to tho depart- 

 ment of meteorology. 



1'HYSIOLOGICAL EFFECTS, ANI> ANIM.U, 

 ELECT1UCITY. 



UNDER the above heading wo shall include some of the 

 physiological effects of electricity, together with a short 

 account of fishes, which have the power of transmitting 

 electric shocks from their bcxlics. Wo shall have to 

 extend considerably on this subject in our ilex- 

 we shall therefore hero confine our remarks to those 

 effects which arc duo to electricity excited by friction, 

 or its a 



/'/'. '.. If tho knuckle be presented to 



sidiictor of an electrical machine, a tingling sensation 

 will bo ex; ik passes. If, however, 



one hand he placed on the knob of a charged jar, whilst 

 the other grasps its external coating, a powerful si 

 will bo felt; which will possibly, if from a pint jar. 

 tend as far as the chest This effect is produced by ihn 

 sudden and powerful contraction of tho muscles. Any 



I See ante, p. ITS; Fig. ft. 



