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with a velocity over 100 miles a second. One of these events has become celebrated for the extraordinary character of the phenomena, as well as for the fortunate circumstance that it has been authenticated by the independent testimony of two skilled witnesses. On the forenoon of the 1st September, 1859, two wellknown observers of the sun, Mr. Carrington and Mr. Hodgson, were both engaged in observation. Mr. Carrington was employed at his self-imposed daily task of observing the positions, the configuration, and the size of the spots by means of an image of the sun upon a screen. Mr. Hodgson, many miles away, was at the same moment sketching, some details of sun-spot structure. They saw simultaneously two luminous objects, shaped something like two new moons, each about eight thousand miles long and two thousand miles wide, at a distance of about twelve thousand miles apart these suddenly burst into view near the edge of a great sun-spot, with a brightness at least five or six times that of the neighbouring parts of the sun, and travelled eastward over the spot in parallel lines, growing smaller and fainter, until in about five minutes they disappeared, after a journey of about thirtysix thousand miles.

We have still to note one very extraordinary feature, which points to an intimate connection between the phenomena of sunspots, and the purely terrestrial phenomena of magnetism. It has been noticed that the occurrence of the maximum of sun-spots occurs simultaneously with an unusual amount of disturbance of the magnetic needle. The latter are well known to be connected with the phenomena of the aurora borealis, inasmuch as an unusual aurora seems to be invariably accompanied by a great magnetic disturbance. It has also been shown that there is an almost perfect parallelism between the intensity of auroral phenomena and the abundance of sun-spots. Besides these general coincidences, there have been also special cases in which a peculiar outbreak on the sun has been associated with remarkable auroral or magnetic phenomena. Thus, the occurrence cited above as witnessed by Mr. Carrington and Mr. Hodgson in 1859, was immediately followed by a magnetic storm of unusual intensity, as well as by splendid

auroras, not only in Europe and America, but even in the Southern Hemisphere. A very interesting instance of a similar kind is recorded by Professor Young, who, when observing at Sherman on the 3rd August, 1872, perceived a very violent disturbance of the sun's surface. He was told the same day by the photographer of the party, who was engaged in magnetic observations, and who was quite in ignorance of what Professor Young had seen, that he had been obliged to desist from the magnetic observations, in con

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sequence of the violent fluctuations of the needle. Subsequent inquiry showed that in England on the same day a magnetic storm was also witnessed.

These observations demonstrate that there is some connection between solar phenomena and terrestrial magnetism, but what the nature of that connection may be is quite unknown, and will form a problem of deep interest for the future labours of astronomers and physicists.

Another mysterious law governs the sun-spots. Their number fluctuates from year to year, but it would seem that the epochs of maximum sun-spots succeed each other with a certain degree of regularity. The observations of sun-spots for nearly three cen

turies show that the recurrence of a maximum takes place, on an average, every eleven years. The course of one of these cycles is somewhat as follows:-For two or three years the sun-spots are both larger and more numerous than on the average; then they begin to diminish, until in about five or six years from the maximum

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Fig. 16.-Dr. Huggins' drawing of a remarkable arrangement of Solar Granules.

they reach a minimum; then the spots begin to increase, and in another five or six years the maximum is once more attained. The cause of this periodicity is a question of the most profound interest, but at present the answer must be regarded as unknown. It has, indeed, to be admitted that the real nature of sun-spots is still a matter of uncertainty. No theory yet proposed will account in a thoroughly satisfactory manner for all the phenomena which

they present, when viewed with the telescope and the spectroscope, as well as for their peculiar distribution over the sun, and the marvellous phenomena of periodicity.

When the atmosphere will allow of very good vision, we can see that the sun's surface is mottled in a remarkable manner. This is well shown in Fig. 15, in which we perceive that the spot in the central part of the picture is merely an enlargement of one of the minute pores with which the surface is marked. A very remarkable instance of the granulated appearance which the sun often presents is shown in a drawing made by the accurate pencil of Dr. W. Huggins (Fig. 16). This curious arrangement has also

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Fig. 17.-The Willow-leaf texture of the Sun's surface.

been witnessed by many other observers. Indeed, photographs have been taken in which these brilliant granules seem disposed to arrange themselves in patterns of marvellous regularity.

It would thus appear as if the luminous surface of the sun was composed of intensely bright clouds suspended in a darker atmosphere. Some observers have thought that these floating objects are, occasionally at all events, of a characteristic size and shape, variously known as "willow leaves" or "rice grains." In Fig. 17, the curious willow-leaf texture is shown surrounding a sun-spot. But the spot itself seldom fails to give the impression of violent disturbance, as is well shown in Professor Langley's fine drawing (Plate II.) of a spot which he observed on December 23-24, 1873.

Near the edge of the sun, as represented in Plate III., will be seen some of those brighter streaks or patches which are called faculæ

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