Part 7 (1/2)

The Sun-Spots are not devoid of motion, and from their movements we learn that the radiant orb revolves upon itself in about twenty-five days This rotation was deter the spots, saw that they traversed the solar disk fro lines that are oblique to the plane of the ecliptic, and that they disappear at the western border fourteen days after their arrival at the eastern edge So invisible for fourteen days, reappears upon the eastern edge, where it was observed twenty-eight days previously It progresses toward the center of the Sun, which is reached in seven days, disappears anew in the west, and continues its journey on the hemisphere opposed to us, to reappear under observation teeks later, if it has not uished This observation proves that the Sun revolves upon itself

The reappearance of the spots occurs in about twenty-seven days, because the Earth is not stationary, and in itsfocus, a motion effected in the same direction as the solar rotation, the spots are still visible two and a half days after they disappeared from the point at which they had been twenty-five days previously In reality, the rotation of the Sun occupies twenty-five and a half days, but strangely enough this globe _does not rotate in one uniform period_, like the Earth; the rotation periods, or movements of the different parts of the solar surface, diminish from the Sun's equator toward its poles The period is twenty-five days at the equator, twenty-six at the twenty-fourth degree of latitude, north or south, twenty-seven at the thirty-seventh degree, twenty-eight at the forty-eighth The spots are usually formed between the equator and this latitude, rees They have never been seen round the poles

Toward the edges of the Sun, again, are very brilliant and highly luenerally surround the spots, and have been termed _faculae_ (_facula_, a little torch) These faculae, which frequently occupy a very extensive surface, seem to be the seat of formidable commotions that incessantly revolutionize the face of ourthe spots They can be detected right up to the poles

Our Sun, that appears so calrations Volcanic eruptions, thestorms, the worst cataclysentle zephyrs coender clouds of fire capable at one burst of engulfing globes of the dimensions of our planet

To compare terrestrial volcanoes with solar eruptions is like coe with the flames of the fire that destroys a town

The solar spots vary in a fairly regular period of eleven to twelve years In certain years, _eg_, 1893, they are vast, nu_, 1901, they are few and insignificant

The statistics are very carefully preserved Here, for instance, is the surface showing sun-spots expressed in millionths of the extent of the visible solar surface:

1889 78 1890 99 1891 569 1892 1,214 1893 1,464 1895 974 1896 543 1897 514 1898 375 1899 111 1900 75 1901 29 1902 62

The years 1889 and 1901 were _minima_; the year 1893 a _netism and the boreal auroras exhibit an oscillation parallel to that of the solar spots, and apparently the saard our sun as a globe of gas in a state of coious alobe is called a _photosphere_ (light sphere) It is in perpetual motion, like the waves of an ocean of fire, whose roseate and transparent flaht This stratum of rose-colored flames has received the name of _chromosphere_ (color sphere) It is transparent; it is not directly visible, but is seen only during the total eclipses of the Sun, when the dazzling disk of that luminary is entirely concealed by the Moon; or with the aid of the spectroscope The part of the Sun that we see is its luitated surface there is a constant ejection of gigantic eruptions, ieysers of fire, projected at a terrific speed to prodigious heights

For years astronoreatly perplexed as to the nature of these incandescent masses, known as prominences, which shot out like fireworks, and were only visible during the total eclipses of the Sun

But now, thanks to an ingenious invention of Janssen and Lockyer, these eruptions can be observed every day in the spectroscope, and have been registered since 1868, more particularly in Rome and in Catania, where the Society of Spectroscopists was founded with this especial object, and publishes monthly bulletins in statistics of the health of the Sun

These proinable forms, and often resemble our own storm-clouds; they rise above the chro 200 kilometers (124 ht of 300,000 kilometers (186,000 miles)

[Illustration: FIG 31--Rose-colored solar flaht, _ie_, 18 times the diameter of the Earth]

The Sun is surrounded with these enormous flames on every side; so roseate plumes; at others they rear their lu leaves of giant pal illustrated a re to submit to the reader a precise observation of these curious solar flames That reproduced here was observed in Rome, January 30, 1885 It hteen tiside in its relative31)

Solar eruptions have been seen to reach, in a few ht of more than 100,000 kilo torrent into that burning and inextinguishable ocean

Observation, in conjunction with spectral analysis, shows these prominences to be due to formidable explosions produced within the actual substance of the Sun, and projecting en into space with considerable force

Nor is this all During an eclipse one sees around the black disk of the Moon as it passes in front of the Sun and intercepts its light, a brilliant and rosy aureole with long, lurettes, which extend a very considerable distance from the solar surface This aureole, the nature of which is still unknown to us, has received the name of _corona_ It is a sort of immense atly, is a brazier of unparalleled activity--a globe of gas, agitated by pheno streamers extend afar The smallest of these flale breath, like the bombs shot out by Vesuvius, that fall back within the crater

What now is the real heat of this incandescent focus? The most accurate researches estimate the temperature of the surface of the Sun at 7,000C The internal teher A crucible of molten iron poured out upon the Sun would be as a stream of ice and snow

We can for certain coiven out appears to be equal to that which would be elobe of the same dihty thousand terrestrial globes), entirely covered with a layer of incandescent coal 28 kilo at equal combustion The heat emitted by the Sun, at each second, is equal to that which would result from the combustion of eleven quadrillions six hundred thousand ether This sa to the boil in an hour, two trillions nine hundred -point

Our little planet, gravitating at 149,000,000 kilometers (93,000,000 miles) from the Sun, arrests on the way, and utilizes, only the half of a milliard part of this total radiation

How is this heat maintained? One of the principal causes of the heat of the Sun is its condensation According to all probabilities, the solar globe represents for us the nucleus of a vast nebula, that extended in primitive times beyond the orbit of Neptune, and which in its contraction has finally produced this central focus In virtue of the law of transformation of motion into heat, this condensation, which has not yet reached its lilobe to its level of temperature, and to maintain it there for millions of years In addition, a substantial nu into it

This furnace is a true pandehs three hundred and twenty-four thousand tihteen hundred and seventy octillions of kilograms: