532 



PHYSICAL GEOGRAPHY. 



feet broad, which encompassed all England as it were. There went out semicircles from 

 the side of it, at whose intersection the four mock suns were situated, the true sun being 

 in the east, and the air very clear. And because this monstrous prodigy cannot be de- 

 scribed by words, I have represented it by a scheme, which shows immediately Jiow the 

 heavens were circled. The appearance was painted in this manner by many people, for 

 the wonderful novelty of it." 



3. Paraselene. Mock moons, depending upon the causes which produce the solar 

 image, or several examples of it, as frequently adorn the arctic sky. On the 1st of 

 December 1819, in the evening, while Parry's expedition was in Winter Harbour, four 

 paraselense were observed, each at the distance of 21^ from the true moon. One was 

 close to the horizon, the other perpendicular above it, and the other two in a line parallel 

 to the horizon. Their shape was like that of a comet, the tail being from the moon, the 

 side of each towards the real orb being of a light orange colour. During the existence of 

 these paraselenas, a halo appeared in a concentric circle round the moon, passing through 

 each image. On the evening of March 30, 1820, about ten o'clock, the attention of Dr. 

 Trail at Liverpool was directed by a friend to an unusual appearance in the sky, which 

 proved to be a beautiful display of paraselenae. The moon was then 35 above the 

 southern horizon. The atmosphere was nearly calm, but rather cloudy, and obscured by 

 a slight haze. A wide halo, faintly exhibiting the prismatic colours, was described round 

 the moon as a centre, and had a small portion of its circumference cut off by the horizon. 

 The circular band was intersected by two small segments of a larger circle, which if com- 

 pleted would have passed through the moon, and parallel to the horizon. These segments 

 were of a paler colour than the first mentioned circle. At the points of intersection 

 appeared two pretty well defined luminous discs, equalling the moon in size, but less 

 brilliant. The western paraselenae had a tail or coma, which was directed from the moon, 

 and the eastern also, but much less clearly defined. 



4. The Rainbow. The most glorious vision depending upon the decomposition, refrac- 

 tion, and reflection of light, by the vapour of the atmosphere reduced to fluid drops, is the 

 well-known arch projected during a shower of rain upon a cloud opposite to the sun, dis- 

 playing all the tints of the solar spectrum. The first marked approximation to the true 

 theory of the rainbow occurs in a volume entitled De Radiis Visus et Lucis, written by 

 Antonius de Dominis, Archbishop of Spalatro, published in the year 1611 at Venice. 

 Descartes pursued the subject, and correctly explained some of the phenomena ; but upon 

 Newton's discovery of the different degrees of refrangibility in the different coloured 

 rays which compose the sunbeam, a pencil of white or compounded light, the cause of 

 the coloured bands in the rainbow, of the order of their position, and of the breadth they 

 occupy, was at once apparent. The bow is common to all countries, and is the sign of 

 the covenant of promise to all people, that there shall no more be such a wide-spread 

 deluge as that which the sacred narrative records. 



" But say, what mean those coloured streaks in heaven 

 Distended, as the brow of God appeased ? 

 Or serve they, as a flowery verge to bind 

 The fluid skirts of that same watery cloud, 

 Lest it again dissolve, and shower the earth ? 

 To whom the Archangel : Dexterously thou aim'st ; 

 So willingly doth God remit his ire 

 That he relents, not to blot out mankind ; 

 And makes a covenant never to destroy 

 The earth again by flood ; nor let the sea 

 Surpass its bounds ; nor rain to drown the world, 

 With man therein, or beast ; but when he brings 



