LESSONS IN LATIN. 



2-1 



appearances. Tho fluctuations of the magnetic needle which 

 occur during their continuance indicate an electrical origin, and 

 thin is further confirmed by the fact that telegraphic messages 

 have been interraptod, and the alarums rung, by the auroral 

 current*. Earth current* are also mnch stronger daring the 

 aurora, and hence it ia now generally attributed to the discharge 

 of elertririty in the upper region* of the air. 



After a thunderstorm a peculiar smell ia nomotimea noticed in 

 the air, similar to that which ia observed near an electrical 

 machine in full work. Thin is due to the production of a sub- 

 stance discovered by Schonbein, and namod by him ozone. It 

 ia now believed to be merely oxygen gas hi an allotropic form. 

 This substance exerts a powerful and beneficial influence on the 

 air, and being a good disinfectant, accounts mainly for the 

 purifying effect of a storm. When, however, it ia present in 

 very large quantities, certain classes of disease are found to be 

 more prevalent than usual. 



Ozone possesses the property of discolouring a piece of paper 

 prepared with iodide of potassium and starch, and the quantity 



degree to which they can be refracted, or beat out of their 

 course. Hence they are separated; the red, being the leas* 

 refrangible, appear at the top in the inner bow. 



In the spray of a waterfall, or even of a fountain, a rainbow 

 may often be seen when the sun is behind the observer. It* 

 rays are, in this case, decomposed by the fine spray, in the same 

 way as they are by the falling drops of rain. 



A lunar rainbow is occasionally seen, and presents a very 

 beautiful appearance ; but unless the moon happens to be near 

 the full, the prismatic colours are scarcely distinguishable. 



Weather prognostics may sometimes be drawn from the 

 appearance of the rainbow. One of these has passed into the 

 proverb 



" A rainbow in the morning 

 Is the nhepherd'i warniug ; 

 A rainbow at night 

 ! the shepherd'! delight." 



A rainbow in the morning must, of course, appear in the 

 west, since it is opposite to the sun, and therefore shows that 



Fig. 13. CAUSE OF THE PHENOMENON OF THE RAINBOW. 



present fn the air is estimated by the extent of this dis- 

 colouration. 



When rain is falling from the clouds opposite to the sun, 

 while it is shining, a rainbow is produced. This consists of two 

 concentric arcs, which ore composed of the seven prismatic 

 colours in just the proportions in which they combine to form 

 white light. In the primary or inner bow, tho violet is on the 

 inner side, and the red on the outer ; in the secondary, this 

 order is reversed. Sometimes only one arc is visible. 



Tho elevation of the bow depends upon tho altitude of the 

 sun. If it bo near the horizon, the bow will be nearly a semi- 

 circle ; but as the sun's elevation increases it sinks and becomes 

 smaller, till it disappears when tho sun attains 42 altitude. 

 For this reason rainbows can only be seen at morning or evening. 



The phenomenon ia a purely optical one ; wo will, however, 

 explain briefly the cause which produces it. When tho rays of 

 tho sun strike on the falling drops of rain, they are first of all 

 refracted, or bent out of their course. Some of them pass out 

 at tho further side of tho drop, but the remainder are reflected 

 from its inner surface, and again refracted as they issue into 

 the air. In Fig. 13 two large drops arc represented, one in tho 

 middle of each bow. In these tho course of tho rays can be 

 distinctly traced, and it will be seen that for the primary bow 

 they only suffer one reflection ; in the outer one they ore twice 

 reflected ; hence its greater faintness. 



Tho different rays which compose white light differ in the 



the clouds are advancing from that quarter which is the damp 

 one while it is clear in the east. The fall of rain, too, at this 

 time of the day, when the temperature is increasing, shows a 

 great humidity of the air, and thus much wet may be expected. 

 The appearance of the bow towards evening shows, on the other 

 hand, that the rain-clouds have passed away to the east, and 

 that it is clearing up in tho west ; fine weather ia therefore to 

 be looked for. 



LESSONS IN LATIN. LVI. 



QUALIFICATION. 



QUALIFICATION takes place between two words when the one 

 modifies the acceptation without changing the form of the other. 

 Thus if I say, scribis bcne, lliov, writcst well ; scribia optime, 

 f 7)ii trrilest excellently, I give two instances of qualification. 

 Of each of these pairs of words, one is a verb, the other ia an 

 adverb. Tho adi-erb is the qualifying word, the verb is the 

 qualified word. The adverb modifies tho verb, for it shows the 

 manner of the action of tho verb. The kind of qualification 

 depends in all cases on the import of the adverb. While the 

 adverb modifies tho meaning of the verb, it does not alter its 

 form. In the last particular, qualification differs from govern- 

 ment ; for government modifies the form as well as the accepta- 

 tion of the word or words that are under its influence. Qualifi- 

 cation differs also from agreement in tho fact that it involves no 



