Junk 30, 1882.] 



KNO^A^LEDGE 



71 



stomach that it will retain under their action what, under 

 other conditions, it would immediately reject Any one 

 unaware of this, who had taken a dose of tartar emetic to 

 cause vomiting after a narcotic had Lcen swallowed in 

 poisonous or almost poisonous quantity, would 1)6 apt 

 to repeat the dose, especially if ignorant of the quantitative 

 poisonous properties of antimony. This, in all probability, was 

 what Mr. Bravo did, until he had taken a poisonous amount 

 of that substance by which he had hoped to get rid of the 

 laudanum he had taken in excess. It was a noteworthy 

 feature of the case that even when his anguish was at its 

 greatest, he would not take laudanum for its relief. 



Be this theory correct or not (for our own part, we have 

 no doubt of its correctness, for the simple reason that 

 every other is in some one or other respect absurdly incon- 

 sistent with the known facts of the case), it is well to know 

 tliat tartar emetic is not suitable in cases of poisoning, 

 though very proper, under medical advice, in other cases 

 where an emetic is required. 



REMEDIES. 



When tartar emetic has been taken in poisonous 

 amount, and vomiting does not follow, it must be excited 

 until, if possible, all the poison has been rejected. Copious 

 draughts of tepid water, tickling the back of the threat, 

 and other such methods of producing vomiting may be 

 employed. If, however, the poison cannot be got rid of in 

 this way, a decoction of tincture of quinine may be given 

 with advantage, for tartarised antimony is decomposed by 

 nearly all bitter or astringent vegetables which contain 

 tannin, producing an inert tannate of the protoxide of anti- 

 mony (which is the active base of tartar emetic and James's 

 Powder). Should no quinine be at hand, a strong infusion 

 of black tea should be administered, pending the arrival of 

 a medical man. 



THE AMATEUR ELECTRICIAN. 



ELECTRIC GEXEEATOES (continued). 

 T"f 'E will now leave our magneto machine in the hands 

 >* of our readers for a time. Possibly their own 

 ingenuity may suggest one or two moditications. One that 

 will reward the extra lal)Our and care involved is, winding 

 the armature with two wires side by side sLmultaneouslj-, 

 so that there will be four ends to deal with. By a simple 

 contrivance the two coils may then be used at pleasure 

 for intensity or quantity — that is to say, we may join 

 them up so as to become one continuous coil, or we may 

 connect the two internal ends together, likewise the two 

 external ends. This latter course is practically doubling 

 tlie size of the wire. The first arrangement would produce 

 comparatively a current of high electro-motive force and 

 small quantity, the second a current of low electro-motive 

 force but large quantity. 



The next step that we may notice in apparatus of this 

 kind is the introduction of electro-magnets in place of the 

 ordinary steel magnets. These may consist of broad, Hat 

 pieces of iron, like those in the Siemens or Brush dynamo 

 machines (that is to say, the width e.xtendiiig the whole 

 length of the pole-pieces) ; or of a series of ii-on rods 

 enveloped with wire, as in the Weston m.ichine. Doubt- 

 less, but few have seen this machine, but they will not go 

 far wrong if they adopt the flat form, winding the iron 

 ■with No. 18 or 'JO cotton-covered wire. Wilde is credited 

 with introducing this form of machine. He used a small 

 machine with permanent magnets to produce the current 

 for magnetising the electro-magnet, and thus obtained in 

 the armature actuated by this electro-magnet a very con- 

 siderable current A small battery will serve the same 



purpose. The smaller machine or battery is generally 

 known as an "Exciter." Its function is apparent It 

 must be remembered that the polarity of the electro- 

 magnets must be on the same principle as that which 

 applies to the use of permanent magnets ; that is to say, 

 the wire must be wound so as to induce north magnetism 

 in one pole-piece and south in the other. It will be ad- 

 visable to use four flat plates 4 in. by, say, C in., and \ in. 

 thick, joining the pairs of free or external ends together 

 by means of iron plates. 



The next discovery was one of vital importance. Those 

 who have had any experience with electro-magnets, even 

 on so small a scale as are used in telegraph instruments, 

 will be aware that, however soft a piece of iron may be, 

 it is almost certain to retain, for a greater or less time, a 

 small amount of magnetism. This is called remanent, or 

 residual magnetism, and Siemens and Wheatstone (simul- 

 taneously but separately) found it sufficiently strong to 

 enable them, by an ingenious arrangement, to dispense 

 with the exciting current It is easily accomplished by 

 the amateur. Join one of the brushes to one of the electro- 

 naagnets (or field magnets), allowing the current to pass 

 thence through the other magnet, and out to one of the 

 terminals. The other brush is connected to the other ter- 

 minal as usuaL What takes place is this : — First, there is 

 a small amount of magnetism in the field magnets ; this 

 induces in the armature a small current, which, being made 

 to pass through the field magnet increases the inducing 

 effect The increased armature current also passes through 

 the field magnet, and so on and on, continually increasing 

 until a very powerful current is obtained. 



This brings us to the end of our descriptions of simple 

 forms of generatoi-s. Before we can go any farther, we 

 must devote three, or perhaps four, articles to a brief 

 account of the various methods of measuring electric 

 currents, and of the units adopted in so measuring, never 

 forgetting, however, that we are writing for amateurs. 



The Telephone i.v Fbaxce. — M. Cochcry, tlio French Ministcr 

 of Posts and Telegraphs, has asked the Cliamber for a grant ot 

 :i50,000 f. to enable him to establish a State telephonic servico 

 between certain towns in France. 



Ax Electric Tramway. — The Portrush and Bushnols Electric 

 Tramway, near Belfast, the first that has been constrnctcd in U><" 

 United Kingdom, will be opened in the first week in August. Tho 

 ceremony will probably be i)erformo«l by the Lord-Lieutenant. 



IXTERXATIONAL TELEGRAPH ST.vn.sTics. — According to statistics 

 recently issued, the length of w^ires in the various countries is o» 

 follows :— Germany, lo'J.UlO miles ; Russia, 134,465 miles: Franc*. 

 125,265 miles; Great Britain, 121,720 miles; .Austria-Hungary, 

 89,960 miles; Italy, 53,692 miles; Sweden and Norway, 2»»,445 

 miles ; Belgium, 16,345 miles, and Switierland, 10,010 miles. Tho 

 total numbers of messages sent during the fmst venr are riasfed an 

 follows :— England, 29,S20,4-I5: tVance, 19.882,»a8; Germany. 

 16,312,457; Austria-LIungarv, S.721t,321 ; Russia, 7,2!»S,422 ; Italy, 

 6,511,407 ; Uolland, 3,100,230 ; and Sweden and Xorwjiy, 2,02»,h06. 



The following should have forme*! part of the first paragraph on 

 p. 63 : — The conclusions arrive<l .it by tho sub-commit fee ore, 1st. — 

 The maximum ctKciency of incandescent lamps in the present statd 

 of the subject, and within tho experimental limits nf this investiga- 

 tion, cannot be assumed to exceed 300 candle-lights per horw- 

 power of current. 2nd. — The economy of all lamps of this kind i« 

 grcoter at high than at low incandescence. 3rd. — The economy pf 

 light-pro<luction is greater in high resistance lamps than in those of 

 low resistance, thus agreeing with the economy of dislributirn. 

 4th.— The relative efliciency of the four lamps txamine.1. cxpre.«scd 

 in Carcel burners of 74 spermaceti candles each. pn>iluied by one 

 horse-power of current, is as follows : — {\.) At 16r.indles : Kdison, 

 265; Swan, 24; Ijine-Fox, 23 5 ; and Maxim, 20' » (U.) At 32 

 candles: Edison, 41-5: Lane-Fox, 37 4 ; Swan, 35 5 : and Maxim. 

 32 4. To doable the light given by these lamps the cnrrcnt-cnrrgy 

 was increased, for the Maxim and Ijine-Fox lamps, 26 per cent : 

 for the Edison lamp, 28 per cent. : and for the Sw:in lamp. 37 p«T 

 cent. 



