208 



THE POPULAR EDUCATOR 



wires arranged as shown by the lines in the diagram. A and B 

 are each of them connected to the binding screw c by the wires 

 A c, B c, which are frequently made of very thin or badly con- 

 ducting wire, for a reason which will shortly appear. The 

 screws A, E and B, K are also connected, and D is joined to both 

 F and H. 



When this arrangement is completed, the wire, or whatever else 

 it is whose resistance is tested, is placed between E and F ; an 

 instrument B, called a resistance coil, is also interposed between 

 H and K. This latter instrument consists of a number of coils 

 of fine and badly conducting wire, the resistance of which is 

 known, and is so arranged that any desired resistance can be 

 caused in it by means of a number of movable pegs. Battery 

 wires are now connected with A and B, and thus it will be seen 

 four ways are made for the passage of the current. It may pass 

 from A to c, and thence direct to B, or along A E F D H K B, 

 going through both resistances ; or it may pass from A, by E F D, 

 then round the galvanometer, and by c to B ; or, lastly, it may 

 take the course A c D H K B. 



Now most of the current would pass along the first and most 

 direct course, ACS, but that a bad conductor is interposed so 

 as to make the resistance as great this way as it is by the third 

 and fourth paths. The second course includes both resistances ; 

 but little, therefore, of the current traverses it, and thus we 

 come to the last two, in both of which it passes through the 

 galvanometer. In one case the wire to be tested forms a part of 

 the circuit, and the current then passes through the galvano- 

 meter in the direction D to c ; in the other the resistance coil is 

 traversed, and the current passes from c to D, or in the reverse 

 direction. These different paths may easily be traced in the 

 diagram. 



Now since the two latter parts of the current are passing in 

 contrary directions round the galvanometer, the needle will 

 remain in its natural position when these currents are exactly 

 equal, as they will be if an equal resistance is offered by each 

 road. In order, therefore, to learn the resistance in the sub- 

 stance to be tested, we must alter that in the resistance coil till 

 the needle comes to its natural position, and then, by reading off 

 from the coils, we shall find what we want. 



German silver wire is usually employed in the manufacture of 

 resistance coils, as it is a very bad conductor, and thus shorter 

 lengths may be employed. The conductivity of the wire to be 

 used is first tested, and a piece is taken of such a length that 

 its resistance is one unit ; this is then made into a coil. Two 

 similar coils are then made with double the length of wire, and 

 a fourth with five times the length. These coils are then con- 

 nected together in a box, after the plan shown in Fig. 28. A, B, 

 c, D, and E represent pieces of brass arranged so as nearly to 

 _ touch. Wedges, like those 



I A't B c " D shown as F, may be in- 



serted between these, and 

 make so good a passage 

 for the current that the 

 coil is quite shut out. The 



Fig. 28. 



coils, consisting respectively of 1, 2, 2 and 5 units, are indi- 

 cated by the number of bends in them. 



Now when wedges are inserted between all the pieces of brass, 

 there is no resistance offered ; but by removing one or more of 

 them we can produce any between 1 and 10. A second series of 

 coils is similarly arranged, each of which offers 10 times the 

 resistance of these 4 ; and a third set, in which it is 100 times 

 as great ; and thus, by means of twelve coils, any resistance 

 from 1 to 1,110 may be measured. ' Four more would raise this 

 to over 11,000 ; but with resistances so great a different kind of 

 instrument is usually employed. 



LESSONS IN SPANISH. VII. 



DEMONSTRATIVE PRONOUNS. 



THE demonstrative pronouns are este, this; ese, that} aquel, 

 that. They are thus declined : 



Singular. 



MASCULINE. FEMININE. 



Este, esta, this. 



Ese, esa, that. 



Aquel, aquella, that. 



Plural. 



MASCULINE. FEMININE. 



Estos, estas, these. 



Esos, esas, those. 



Aquellos, aquellas, those. 



There is also, in the singular number of each of these 



demonstrative pronouns, a neuter form, used when we cannot 

 ascribe a gender to it ; viz., esto, eso, aquello. 



Este is used with what is near at hand ; as, este hombre, this 

 man (here) : ese with what is somewhat distant ; as, ese hom- 

 bre, that man (there) : and aquel with what is still more dis- 

 tant ; as, aquel hombre, that man (off there, yonder). When 

 relating to time, este is used with time present ; ese with time 

 past ; and aquel with time still more distant ; as, " this (este) 

 book which I now have, that (ese) book which I had last week, 

 and that (aquel) book which I had last summer, are valuable." 



Este refers to the last mentioned of two things, and ese (or 

 aquel) to the first ; as 

 El general y el capitan vinieron ; The general and the captain came ; 



ese (or aquel) es prudente, este the former is prudent, the latter ia 



es fatuo, stupid. 



When este or ese comes before the indefinite pronoun otro 

 (other), the former drops its final letter, and the two are joined, 

 forming one word ; as, estotro or estotra, this other ; estotros or 

 estotras, these others ; esotro or esotra, that other ; esotros or 

 esotras, those others. 



If the objective case of the relative pronoun quien (whom) ia 

 used in such phrases as he whom, she whom, him whom, etc., 

 aquel must come before it ; as, aquel a quien, he whom ; aquella 

 a quien, she whom ; aquellos or aquellas a quienes, they ivhom; 

 as 

 Aquellos contra quienes pelearon, Those against whom they fought. 



When the relative pronoun of the objective case is not pre- 

 ceded by a preposition, the definite article is generally used 

 instead of aquel, and is followed by the relative pronoun que ; 

 as, el que, he whom ; la que, she whom ; los or las qne, they 

 whom. Thus it will be perceived that he whom may be rendered 

 either, aquel a quien or el que ; she whom, by either aquella a 

 quien or la que ; they whom, or those whom, by either aquellos 

 or aquellas a quienes, or los or las que. The latter mode is 

 most generally employed. 



When the objective case of the personal pronouns him, her, 

 or them precedes the nominative of the relative who, either 

 aquel or the definite article may be used ; as 



Juan di6 pan a aquella que tiene John gave bread to her who t 

 hambre, or Juan dio pan a la hungry. 

 que tiene hambre, 



When in English the demonstrative pronoun that is followed 

 by the preposition of, and refers to a noun already expressed, the 

 definite article is employed in Spanish ; as 



For su prude'ncia y por la del Through his prudence and through 

 juez, that of the judge. 



The English demonstrative pronoun thai is rendered in 

 Spanish by the definite article when it refers to something 

 having preceded it and is followed by the preposition of ; as 



My house and that of my servant, Mi casa y la de mi criado. 



His only desire was that of free- Su imico desito era el de libertar d su 



ing his country from the Sara- patria del yugo sarraceno. 



cen yoke, 



The soldiers of General Brown are Los soldados del general Brown son 



as brave as those of General tan valientes como los del general 



Canrobert, Canrobert. 



VOCABULARY. 



Posadero, in?ifceeper. 

 Pronunciacion, pro 



nunciation. 

 Soinbrerero, hatter. 

 Tenedor, fork. 

 Vino, wine. 

 Zapatero, shoewafcer. 

 Zapato, shoe. 



MODEL SENTENCES. 

 Aquellas mugeres tienen pruddn- Those women have prudence. 



cia, 



Juan hablo a aquella a quien vm. John spolce to her tchom you saw. 

 vi6 ; or, Juan hablo a la que 

 vm. vio, 



EXEKCISE 17. SPANISH-ENGLISH. 



1. Este hombre es rico. 2. Aquella rnuger es soberbia. 3. ,J Habla 

 esa senora la l^ngua= inglesa 1 ? 4. 4 Cuyo es este cuchillo ? 5. j Cuyos 

 son esos tenedores? 6. Aquel a quien mi padre escribio las cartas 

 tiene mucho dinero. 7. Aquella a quien Juan dio un libro es nray 

 hermosa. 8. Esta casa y la que vmd. viu, sou mias. 9. j No es este 



