| Show electricity wi present herewith a full report ast lecture on electricity under the auspices of the ao gents society of the salt lake awe A academy by prof jas E raae the publication of the 0 has been intentionally de ya for saras little time so BO that N k wild immediately precede the report of prof balmages Tal mages second lecture on the same subject which was delivered a week ago and will be published in an early issue ed the title applied to the lecture of the evening is so broad and comprehensive p that we can hope to do little more than consider its general outline it was some years before the time of christ that the grecian philosopher thales rubbed a bit of amber on silk and wondered at the result we will repeat his experiment here is a bit of amber in which by the way a fossilized beetle has been preserved in all its natural brilliancy of hue I 1 rub it briskly on a silk handkerchief and now as aa y you on see it attracts this bit of wool and this tiny feather much asa as a magnet or loadstone attracts a needle this simple process precess when first performed was the means of suggesting others by way of farther trial and before long it was known that many substances shared with amber this peculiar property the greek word for amber was electron and from that our term electricity has been derived it was not dot till 1600 A D that any system or classification was attempted in the study of this peculiar force but in the year stated dr gilbert of colchester england published an extended list of substances possessing the electric property like amber I 1 hold in my hand a glass rod also a dark colored piece of silk both have been slightly warmed so as to prevent the condensation of any vapor from the atmosphere of the room I 1 bring as you see the glass rod near this little ball of elder pith suspended by a silk thread from a convenient hook no striking effect is produced now I 1 rub the glass vigorously with the silk and once more approach the suspended ball of pithy pith now you par perceive that the ball is drawn towards the rod fig figl 1 there is no special virtue in the pith ball used in this experiment other than that of convenience fig 1 electric attraction any light substance would answer a bit of cork cark or a shred of paper or as you see here a hollow ball of brass though in this last instance the ball being heavy considerable friction must be bestowed on the rod before its power of attraction is sufficient to move the ball let us now carefully repeat the experiment with the ball of pith as before the the ball is drawn toward the excited glass rod it touches the rod now clings to it for an instant and is then driven forcibly away As I 1 fig 3 2 electric bring the rod 0 onca more near you notice that the ball baill to Is strongly re polled fig 2 the bit of pith seems now as eager to avoid contact with the rod as it was before to touch it this is the characteristic of all electrically excited bodies at first they attract and then vigorously repel any light articles in the vicinity here is a rod of vulcanized rubber an ordinary rubber ruler in fact we may rub this with flannel or woolen cloth but better still with cats you see me do now As I 1 bring this ruler near the pith balls as before they are first attracted and then repelled to vary the demonstration I 1 rub the ruler again and bring it near the table upon which have been placed some bits of paper feathers specks of bran and the like pig fig 8 3 fig 3 the excited ruler baler these tiny particles spring from the table to the ruler with eager haste and then are driven away again here now is the pith ball which the glass rod repelled so vigorously a few minutes ago agg you see that the vulcanite ruler attracts it strongly to make sure we see the manifestation aright I 1 rub the glass rod once again with silk and bring it near the pith yes the ball is 18 repelled by the glass and attracted by the vulcanite this second ball is as you perceive attracted by the vulcanite and repelled by the glass it would seem then that we are dealing with two different kinds of force or at least some force under different and indeed opposite characteristics acte the early experimenters noted this difference too they used principally rods of glass and sticks of resin or sealing wax and they named the electricity developed by rubbing glass with silk vitreous electrically electric aly and that excited by friction on resin they called kemnow eddric electricity for the sake of convenience we speak now of the former kind as post tive and represent it by the plus sign and the latter we call negative and designate ibby it by the minus sign As soon as the pith ball had actually touched the excited rod and had become charged as we may say with the same variety of electric force as the rod itself repulsion occurred in fact this is always the case and it is a common rule that wee AW repel and unice attract we have here a pair of pith balls suspended from the same hook hoek you see they hang side by side in perfect agreement I 1 bring this rod of shellac already rubbed with cafe caas skin near the pair they are both i drawn by this mysterious power of attraction near the rod they touch it now they are repelled having partaken partaker par taken of the same electrical excitement cit as that of the rod itself but you notice fig 4 that the two pith balls now exhibit a strong repugnance toward each other mg fig 4 mutual repulsion they are charged with the same kind of electricity resinous or negative from the resin stick and consequently they repel this simp simple le piece of apparatus reveals the exi existence existent stene e of electric excitement and in consequence may be I 1 termed an electroscope but a I 1 much more sensitive instrument may be constructed without much trouble here is a glass bottle fig 6 5 through the top a rod of brass passes terminated above by a knob and ending below in a pair of thin gold leaves V pig fig 0 5 goldleaf gold leaf electroscope whenever I 1 bring an excited body near as you see the leaves diverge and if the body be highly charged the tiny strips of gold are thrown into a paroxysm of excitement they seem to be fairly wild the explanation is simple suppose we approach with the rubbed glass charged as we know with vitreous or positive electricity the nega tive electricity is drawn too to the point nearest the rod while the positive is repelled to the farthest limit which in this case is the 00 leaves and consequently they diverge with this instrument we can readily prove the development of electricity in many of our commonest operations I 1 have here a rod of copper suspended in a stirrup formed DY by doubling a silk handkerchief one end of the copper rod to is in contact with the electroscope and the other end I 1 approach with the rubbed resinous stick the leaves diverge although the distance of the excited resin is so great that we were no copper rod interposed the influence would never be shown by the gold leaves here is a rod of glass of about the same length and size as the copper rod I 1 place that in the stirrup and bring one end in contact with the telescope while the excited stick of resin is at the other end no divergence of the leaves is seen showing plainly that the electric influence can be transmitted through the particles of the copper rod from one end to the other but not so with the glass substances resembling the copper just used i 1 e those that allow the passage of the electric influence are called conductors while others through which the electric power powe seems unable to make a passage sl are called non the chief af conductors in the order of their efficiency are silver copper gold brass tin iron lead platinum ger man silver charcoal metallic ores water alcohol paper living plants and living animals the common comMO 11 est eat non conductors are fats W wa glass silk rubber furs amber resin parchment and porcelain it will be noticed that all the gub bab stances thus far used for exciting i electricity by friction belong to tn th class of non conductors and at 01 one time it was supposed that these weta the only bodies capable of such e 4 s cit ement in consequence of non conductors were called electa i and conductors were termed 00 eleo ek fries etries let us examine the merits of sa baj cb a distinction here is a good d brass tube I 1 rub it vigorously ww with silk while holding it in the hand band and bring it near the electroscope electro signs of electric excitement aphea appe 1 I try rubbing with flannel flanna then with cloth then with cats cate skin Is to each case with a similar result it would wem then brass is not susceptible of U f elects excitement suppose horev however ver w try ty again after afar providing the brass tube tobe A with a non con ducting or an insulating formed by thrust g b itta a glass rod inside the ro brass braes tube while holding u the handle I 1 now rub the 1 bass and by bringing lt it q ilear ear the electroscope we j V a very vigorous a 0 divergence er gonce of the leaves arx rhe ie electric power was un developed even S 0 before but it escaped B through my body to the w earth ah the insulating handle p of klass glass however prevents this his escape I 1 take now an ordinary hard bard rubber comb a few strokes across this ta s fur fur and the comb causes great did Bt when brought near the a here is a sheet of ung paper I 1 place it on a warm board oaid and rub it with a simple pencil Pel lell eraser the paper clings now 86 80 tightly to the board by virtue of tho e electric attraction that it can difficulty be removed I 1 hold old this sheet of paper near the wall and though large and heavy it clings to the wall I 1 have here 0 also o a sheet of ordinary brown aft wrapping ang paper this 1 draw several abal ates between my arm and the side aide bemy bf my body it is now electric electrically aDy eted through this friction and es to the wall as you see I 1 hold waa 18 sheet of paper over the head of this s gentleman and sitting near me each particular hair now stands on bu bud d I 1 take another sheet of aver aper and excite it by rubbing as bufore ore but before taking from the board d I 1 cut it into shreds about four our vf abts of its length on removing paper from the board each shred repels the others another example of 01 electrical repulsion behave we have spoken here only of at alon and repulsion as proofs of electric elect lic excitement if however theas oege little experiments had been eln in a dark room in every case cam a able spark accompanied by a ing noise would have passed from th the excited body 1 will ask gentleman who aa kindly promised to assist me to toted upon this stool which is formed ned with glass legs so as to pret Vent electrical communication with theft e rth I 1 place e about his dea this chis rubber cloak it is a ladys lady 1 atit however and does doe s not fit him bim I well wella as eit it might now I 1 thrash toa ha as 48 you see me with this cats skin x 11 bush 8 experiments it is always 0 the cat from flom the skin tot ave e already done with this one CC otherwise pussy might object I 1 bring the electroscope near the gen clemans tl emans hand and the instrument indicates a most powerful excitement I 1 bring my hand near the gent lemans nose and a brilliant spark passes between his nose and my hand those sitting near could doubtless hear the sound of the discharge and judging from the gent lemans somewhat some what queer contortions he felt the passage we will we must adopt some easier way of generating electricity however we have here fig 7 an instrument known is as the it consists of a cake of wax or vulcanite B and metallic sheet A provided with au insulating handle of glass by rubbing or striking the upper surface of the vulcanite with flannel or fur and then placing the metallic plate upon it taking care to touch the metal while in I 1 fig 8 electric machine use the cats skin about his shoulders once more and ask him to then bring his knuckle near the burner i from which wh ich the gas is escaping escabi ng As A s he does so a spark passes to the burner and lights the gas if the room were not so warm we could easily light the gas by touching the burner with an icicle held in the hand band after having become electrically tri cally charged often a pe person may become electrified by simply shuffling about a carpeted room in woolen stockings without shoes sufficiently to light gm gas in the same way and it is said blasts have been prematurely exploded x in mines through the workmen rubbing against the walls as they walk and then accidentally touching the wires leading to the powder AO fig 7 contact with the vulcanite then lifting the plate by its glass handle a very strong spark can be drawn from the plate and this can be many times repeated without a repetition of the striking the first true electric machine was constructed by the renowned otto von guericke in 1672 it consisted of a globe of sulphur revolved by means of a crank while the hand of the experimenter ex p eri menter or a pad of silk was pressed against lt it later glass globes were used instead of sulphur then glass cylinders were employed imp loyed in place of globes and lastly plates of gla glass we have here the latest and most efficient form of machine fig 8 in which as you see there are two glass plates one being stationary and the other being made to revolve with great rapidity it is called from its inventors the holtz machine As you readily see when the movable plate is rapidly revolved sparks several inches in length pass between the poles here then are brilliant luminous effects in addition to the mechanical effects of attraction and repulsion already illustrated whenever the free passage of the electric force is interrupted a luminous manifestation to is the result by darkening the room we can perceive such much better now when the poles of the machine are tolerably close together A fig pi 9 a straight spark is the result A C fig 9 electric sparks when the poles are farther apart B a sinuous spark is seen and when still farther C a zigzag course is followed by the electric force The these sesame same varieties of discharge may be seen in the lightning flashes here is a plate of glass on which a strip of tin foil has been pasted and then cut through in the shape of a flower vase when connection is made with the machine a spark appears at every cut and the figure of the vase is clearly seen here too to is a long glass tube fig 10 on a convenient stand with bits y of tin foil pasted on the inside in a spiral form sparks arke appear between the X tin foil discs disco when the connection is made and the spiral figure flashes out in startling brilliancy but perhaps the most beautiful of luminous effects may be realized by passing the current pig fig 10 through a tube eon con spiral tube a ramified rarified gas these tubes are made in great variety of form and are named from the inventor geissler tubes several are here connected and as the current passes you see them become luminous through the incandescence of the enclosed gas and the result is one of indescribable beauty fiall Fig ll 11 S fig 11 geissler tubes every imaginable tint of the rainbow seems to be represented here in tremulous waves of light the room being now re lighted we can examine some other effects of this mysterious power here are three bells pig fig I 1 12 2 two of them suspended by chains from a metallic crossbar cross bar which I 1 connect with the machine the middle bell however is insulated by a silk thread a chain connecting with the earth or the other pole of the machine As the machine Is operated the little hamm hammers which are hung by silken threads pass back and forth being alternately attracted and repelled by the outside and middle bells and produce a merry jingle not entirely of sleigh bells fig 12 electric hime here too is a vessel something like a bottle though instead of a |
