398 



THE POPULAR EDUCATOR. 



suddenly vanishes. Some observers have even seen the bright 

 edge of the lunar disc outside the star before it vanished. This 

 phenomenon has puzzled astronomers considerably, as no 

 altogether satisfactory explanation of it has hitherto been 

 advanced. Some have supposed it to be an optical illusion, 

 depending partly upon the imperfect nature of the lenses em- 

 ployed; while others have attributed it to the different refrangi- 

 bilities of the light from the star and from the Moon. By 

 means of a telescope these occultations can easily be observed. 



Bare instances have been recorded in which one planet has 

 eclipsed another, or a star, but in some of them it seems pro- 

 bable that they were merely in such close proximity that they 

 appeared as one. 



When planets happen to be very near together they are said 

 to be in conjunction. It is not unusual for two planets thus 

 to be in close proximity. Seldom, however, are several thus 

 side by side. In September, 1186, the rare phenomenon of 

 Mercury, Venus, Mars, Jupiter, and Saturn being all in con- 

 junction, was observed. Ages must elapse before this can occur 

 again. 



Before passing on to notice the main facts relating to the 

 stars, it will be well just to glance at the instruments employed 

 by the astronomer in his researches. The most important of 

 these is the telescope ; in fact, it may be said that in nearly all 

 his instruments the most essential portion is a telescope, the 

 mode in which it is mounted varying according to the special 

 purpose for which it is intended. 



A full description of the principle on which the telescope 

 acts will be set before the student in a future lesson. Two 

 objects are sought to be obtained by the use of this instrument. 

 The one is to collect a much larger number of rays of light than 

 can enter the unaided eye, and thus to render the illumination 

 much greater, and discern objects too faint to be seen other- 

 wise. The other is to cause those rays to enter the eye at a 

 larger angle, and thus make the object appear larger than it 

 does to the naked eye. 



To accomplish these objects two different kinds of instru- 

 ments are employed the refracting and the reflecting telescope. 

 The former consists essentially of a double-convex lens of con- 

 siderable focal length, called the object-glass. The rays of light 

 which fall on this are by it brought to a focus, and a second 

 lens magnifies the image thus formed. Fig. 39 will illustrate 

 this, o being the object-glass, which forms an image at A B, and 

 E the eye-piece, which magnifies the image. The largest refract- 

 ing telescope yet made has an object-glass 25 inches in diame- 

 ter, and it will easily be seen how great must bo the amount of 

 light received by this when compared with the pupil of the eye, 

 which is only one-fifth of an inch across. Earl Rosse's tele- 

 scope, already referred to, is the largest reflector ever made, its 

 speculum having a diameter of 6 feet. Telescopes of this kind 

 consist of a long open tube, with the speculum placed at the 

 lower end. The observer then looks in through a lens placed at 

 the open end, or at one side. 



The instrument usually employed when we want to examine 

 the position of any celestial body is that known as a transit 

 instrument, and represented in Fig. 40. Two pillars of solid 

 masonry carry the bearings of the horizontal axis of the tele- 

 scope. This axis points due east and west. The telescope, 

 therefore, which is at right angles to it, describes a great circle, 

 passing through the north and south points of the horizon, and 

 also through the pole of the heavens. Every star will therefore 

 be visible in the telescope at the time of its culminating or 

 crossing the meridian. Those circumpolar stars which never 

 set will also be visible during their lower passage of the meri- 

 dian. 



Great care is required in the mounting of this instrument to 

 ensure the tube being directed due north and south. The tele- 

 scope is sometimes taken out of its bearings and reversed, so as 

 to ascertain whether it is correctly adjusted ; and then, if the 

 tube be not at right angles to the axle, it will at once be de- 

 tected. The polar star also affords another means of testing 

 the instrument, for, as it is not situated directly at the pole, it 

 describes a small circle round it, and the visual ray of the tele- 

 scope should divide this circle into two equal portions. If, then, 

 we notice three successive upper and lower transits, and the 

 intervals between them are exactly equal, we may conclude that 

 the instrument is correctly adjusted. The weights shown in the 

 figure relieve the bearings of a portion of the strain. 



READINGS IN LATIN. XII. 



TEIiENCE. 



P. TERENTIUS AFEK, the greatest master of Roman comedy, 

 flourished some years after Plautus, whose comedies were noticed 

 in the previous Readings, and whom he excelled in greater 

 purity of diction and finish of style, though he cannot be 

 credited with greater originality than his predecessor, being 

 equally dependent with him upon Greek sources for the form 

 of his plays, the outlines of their plots, and the names and 

 individuality of his characters. He is said to have lived at 

 the end of the second Punic war, and to have been a Cartha- 

 ginian slave, which latter statement is borne out by his name, 

 Afer (the African). He is only known to have written six plays, 

 all of which have come down to us, and which bear the fol- 

 lowing titles "Andria," "Hecyra," "Eunuchus," " Heauton- 

 timoreumcnoa," "Adelphi," " Phormio." It is needless to give 

 in detail the plots of any of these ; they none of them give a 

 very high idea of the morality of the age, and principally turn 

 on lovers' intrigues, the father's wrath a serious thing in a 

 country where the father was allowed absolute control over his 

 children and the shifty machinations of ingenious slaves, 

 whose cunning, if not always successful, is generally the most 

 amusing element in the piece. 



A few words are necessary to explain the following extract 

 from the "Andria." Pamphilus, son of Simo, has fallen in 

 love with Glycerium, a native of the isle of Andros hence the 

 title of the play. Hia father, hearing of it, and thinking the 

 marriage not likely to be a very creditable connection, orders 

 him to marry the daughter of his old friend Chremes. Davus, 

 the slave of Simo, who has a plot in his head for setting mat- 

 ters right, induces Pamphilus to profess submission, and it 

 accordingly becomes known that Pamphilus is to marry the 

 daughter of Chremos (Philumena), with whom Charinus, a 

 friend of Pamphilus, is already in love ; and Byrrhia, the slave 

 of Charinus, has just informed him of the report. 



ANDRIA, ACT II., Sc. 1, 1. 2 28. 

 CHARINUS. BYBBHIA. PAMPHILUS. 



CH. Va misero mihi. 



lit animus in spe atque in timore usque antehac adtentusfuit, 

 Ita postquam adempta spes est, lassus, cura conf ectus stupet. 

 BY. Quffiso edepol, Charine, quando non potest id fieri, 



quod vis, 5 



Id velis quod possit. CH. Nil volo aliud nisi Philumenam. 



BY. Ah, 

 Quanto satius 'st te id dare operam, qui istum amor em ex 



corde eiicias ; 



Quam id loqui, quo magis lubido frustra incendatur tua. 

 CH. Facile omnes, cum valemus, recta consilia segrotis 



damus. 

 Tu si hie sis, aliter censeas. BY. Age, age, ut lubet. CH. Set 



Pamphilum 10 



Video. Omnia experiri certum 'st prius quam pereo. BY. 



Quid hie agit ? 

 CH. Ipsum hunc orabo : huic supplicabo : amorem huic 



narrabo meum : 



Credo impetrabo, ut aliquot saltern nuptiis prodat dies 

 Intcrea fiot aliquid, spero. BY. Id aliquid nihil est. CH. 



Byrrhia, 

 Quid tibi videtur ? adeon' ad eum ? BY. Quid ni ? nihil 



ut impetres, 15 



Ut te arbitretur sibi paratum mcechum, si illam duxerit ? 

 CH. Abin' hinc in malam rem cum suspicione istac, scelus ? 

 PA. Charinum video. Salve. CH. O salve. Pamphile, 

 Ad te advenio, spem, salutem, consilium, auxilium expetens. 

 PA. Neque pol consili locum habeo, neque ad auxilium 



copiam. 20 



Set istuc quidnam 'st ? CH. Hodie uxorem ducis ? PA. 



Aiunt. CH. Pamphile. 

 Si id facis, hodie postremum mevides. PA. Quidita? CH. Ei 



mihi, 

 Vereor dicere : huic die quaeso Byrrhia. BY. Ego dicam. 



PA. Quid est ? 

 BY. Sponsam hie tuam amat. PA. Ne iste haut mecum 



sentit. Ehodum die mihi : 

 Numquidnam amplius tibi cum ilia f uit Charine ? CH. Ah, 



Pamphile, 2o 



