THE SUN AND SOLAK PHENOMENA. 55 



was not till telescopic views had been obtained, that the apparently smooth, unchequered, 

 uniformly luminous face of the sun was found to be an illusion. The discovery of the 

 vast and mysterious peculiarities, called the solar spots, is due to Galileo, though it has 

 been claimed by and for other observers. They were first discerned by him in April, 

 1611. In a letter published in the following year, he announced their irregular and 

 variable figures, the unequal term of their continuance, their motions across the disk in 

 parallel lines, and their confinement to a narrow zone north and south of the sun's 

 equator. Scheiner, a German Jesuit ; and Fabricius, the friend of Keppler, observed them 

 about the same period, but not with the accuracy of Galileo. Being unacquainted with 

 any method of intercepting a portion of the solar rays to save the eye, Fabricius could 

 only observe the sun at the horizon, when his brilliancy was impaired by the density of the 

 atmosphere, and even then he suffered much from the impression of the solar light. Our 

 own countryman also, Harriot, the companion of Raleigh in his voyage to the New World, 

 must be ranked among the first observers of these phenomena, the discovery and study of 

 which have contributed to correct former opinions respecting the physical constitution of 

 the great orb of day. Though ordinarily to the unassisted sight the sun exhibits a face 

 of uniform and dazzling splendour, yet instances are recorded of his tarnished surface 

 being perceptible to the naked eye. Herschel, who intently studied solar phenomena, and 

 lost one of his eyes through the intense glare, mentions a spot appearing in the year 1779 

 large enough to be thus discerned. This may explain and justify some statements which 

 have been regarded with incredulity. Thus, we have it upon the authority of Plutarch, 

 that, in the first year of the reign of Augustas, the sun's light was so greatly diminished, 

 that the unprotected eye might steadily contemplate his orb. Abulferagius also relates, 

 that, in the ninth year of Justinian, the sun suffered a diminution of his light, which 

 lasted above a year and two months ; and that, in the seventeenth year of the emperor 

 Heraclius, half of his body was obscured, which continued from the first Tisrin till 

 Haziran ; that is, from October to June. Keppler likewise states, that once in his time 

 the solar aspect was strangely altered, as though a thick haze enveloped his body ; and 

 the stars shone out at mid-day. Hakluyt gives the following entry from the log of a ship 

 on the coast of Africa in December, 1590 : " The 7th, at sunset, we saw a great black 

 spot on the sun ; and on the 8th, both at rising and setting, we saw the like, the spot 

 appearing about the size of a shilling." 



The spots are all evanescent, but some are sufficiently permanent to be recognised as 

 the same after the lapse of a considerable period. They appear upon the eastern edge 

 of the sun, and move towards the western, vanishing when its edge has been gained, 

 reappearing at the eastern extremity in about thirteen days and a half, to pursue the same 

 route. When first seen upon the eastern limb they scarcely seem in motion, afterwards they 

 appear to travel slowly, their velocity increasing till the central regions have been passed, 

 when they apparently relax, and gradually disappear at the western extremity. This is 

 obviously an optical illusion occasioned by the oblique direction in which we view the 

 marginal parts of the sun's body. The fact sensibly demonstrates the solar rotation ; but 

 the period included between the appearance of a spot at the eastern edge and its return 

 thither, is greater than the real time of one rotation, owing to the earth advancing all 

 the while in its orbit. The apparent interval of revolution is rather more than twenty- 

 seven days ; the true time of rotation is somewhat less than twenty-five days and a half, 

 a much longer period than that taken by our own globe, 'harmonising with the mightier 

 dimensions of the solar machine. The end accomplished by the sun having a motion of 

 rotation upon his axis is inscrutable to us. The planets revolving round a central body, 

 the source of light and heat, rotate upon their axes in order to bring the various parts of 

 their surface under the action of the solar beams. But the reason will not apply to a 



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