AN APPROACHING TOTAL SOLAR ECLIPSE.
AN important total Solar Eclipse will occur on April 5.. Unfortunately, the path of total shadow lies for the most part on the Indian Ocean, and the totality will last longest at a. place in the open seas due south of the Indian Empire. Still, a
portion of the line of totality crosses the land, meeting the- peninsula of Farther India close by Tenasserim, and passing thence over Bangkok, the capital of Siam, to Hue in Cochin China; after which, skirting the island of Hainan and traversing the Bashee Islands (between Formosa and the largest of the Philippine- Islands), the track of totality passes onwards to the Pacific, where- the shadow leaves the earth. Before reaching Farther India, however, the shadow crosses the group of islands called the- Nioobars, between Sumatra and the Andamans ; and it is here that the most favourable places, in an astronomical sense, are to be found for observing the eclipse. For at Kaikul, in the Nicobars, totality will last very nearly 4i minutes. At Mergui, the chief island of the Mergui Archipelago, totality will last more than four minutes ; at Tenasserim (in British Burmah) only three seconds leas than four minutes ; while lastly, at Bangkok the duration will be 3 minutes 54 seconds. Remembering that in the Mediterranean eclipse of December, 1870—during which, notwith- standing unfavourable weather, results of great value were obtained —the totality nowhere lasted more than two minutes, we see that the occasion is one of great importance to science. The Royal Society had already taken up the matter, and a Committee of that
body was inquiring into the best way of approaching Government with requests for aid in money and ships, when a letter came-
from the King of Siam'inviting astronomers to visit his capital, offering to erect suitable observatories for the occasion, to enter- tain the scientific visitors as his own guests, and in fact, making proposals which amount, as the Times correctly says, to the " offer of a large subsidy " to science. The Indian Government has also placed a ship at the disposal of observers who may wish to be sent to the Nicobar Islands or the coast of Burmah, and it is considered likely that the Admiralty will have a ship at Singapore ready to take any observers who accept the King of Siam's- invitation.
We trust our Government will act generously in this matter. There are many interesting questions in Solar physics which yet await solution ; and although modern methods of research enable astronomers to investigate some of the solar surroundings without the aid of an eclipse, yet the Corona still remains beyond their scrutiny save when, in total eclipse, not only the light of the sun's orb is concealed, but our own atmosphere—whose bright- ness ordinarily hides from view the outskirts of his domain—is.
thrown into shadow. Then and then only the Corona, springing suddenly into sight, discloses for a few brief minutes its wondrous- structure. Behind the veil of light formed by our air under solar illumination that marvellous solar appendage exists all the time, undergoing changes of figure which, could we but see them, would afford significant evidence of the relations of the corona to the great central orb. It may be that, one of these days, means
may be found to bring the corona into view, even as the promin- ences can be seen, without the aid of an eclipse. But as yet this has not been achieved, and we have to be content with what we can learn during total eclipses of the sun.
Already much has been learned respecting the Corona, by the use of modern scientific appliances. The spectroscope has told us that the corona shines partly with its own light, and partly by reflecting the light of the sun. Its own inherent light is such, under spectroscopic analysis, as to show that the corona consists, in part, at any rate, of glowing gas. The reflected sunlight gives, of course, the ordinary solar spectrum, and tells us nothing of the constitution of the matter reflecting it ; nevertheless, as the glowing gas of the corona would not reflect sunlight very effect- ively, we may assume that in all probability a portion of the .1` coronal light is reflected from solid or liquid bodies travelling near the sun, like the flights of meteors which, even at our greater distance, the earth occasionally encounters. The corona has also been photographed by Brothers and Winlock in 1870, and by Tennant and Davis (the photographers of Lord Lindsay's expedition) in 1871, and unexpected and as yet unexplained peculiarities have been revealed in its structure.
It might, perhaps, seem that since we now know what the Corona is, what it consists of, and the peculiarities of its structure, we can scarcely hope for any new results of importance during the coming eclipse. What can be done, many may be disposed to inquire, but to examine the coronal spectrum afresh, or to photograph the corona,—in a different aspect, no doubt, but still with very small chance of detecting any novel appearance? If astronomers are satisfied with former observations, some may ask, why should they set out to observe this coming eclipse? and if they are not satisfied with them, why have they attached so much importance to the observation of former eclipses?
But the fact is, that astronomers have new questions to address to the Corona during totality, and new methods of observation to employ. They have not been idle during the last three years ; and in fact it may fairly be said that, during that time, the whole aspect of the subject has changed, or, at least, that the true aspect of the subject has been much more clearly recognised than of yore. The astronomer perceives more and more clearly the close interdependence of the various phenomena with which not his science alone, but science generally, has to deal. The old manner of viewing the celestial bodies, as so many orbs each having such and such peculiarities, is passing away by slow degrees. The astronomer no longer gives his chief attention to examine in what respect this or that celestial body is distinguished from others, but inquires what position the several orbs bear in the scheme of creation. He perceives that the various members of the solar system represent different stages through which every orb in the universe has probably passed, or will pass hereafter. He sees that among the various suns which we call stars, there must be many that resemble our own sun, many which illustrate other stages in the life of suns, and doubt- less many belonging to different orders in the scheme of the universe. The study of the sun, then, has come to have a new significance. For we see in the sun an orb in a stage of existence such as the giant planets have known, and such as our earth, and even the moon and other small members of the solar system, have passed through at still remoter periods of their history. We also recognise in our sun's present condition a stage in the history of a planetary system growing from a nebula to a scheme of worlds ruled by a central orb. We see in the sun the one star we can closely examine, the one body which can give us trustworthy evidence respecting the component members of that system of bodies next higher in order to the planetary system—the galaxy of stars. It is, then, not solely to inquire what the corona, viewed as a solar appendage, is like, or how it is constituted, that the astronomer now approaches the study of the eclipsed sun ; but to ascertain what evidence it affords respecting the past condition of our solar system, respecting the present condition of the sun as a still developing body, and respecting the probable condition of the domains immediately surrounding the other suns which people space. We have learned to look on the sun not as a mere globe limited by its visible extent, but as the resplendent centre of a far larger mass—not globular at all, but extending mighty arms of gaseous and meteoric matter into surrounding space. We no longer regard the sun as mighty merely by the enormous attractive energy residing in his globe, but as a giant rejoicing in a mighty life. We see in him the still growing nucleus of the vast nebula from which our system was formed. He is not only the source of that heat which is the life of the solar system, but is himself instinct with an inconceivable vitality. It is in this aspect that the study of the solar surroundings is so full of in- terest. The astronomer will watch the corona during the ap- proaching eclipse with a new interest, because he will recognise in it no mere appendage, but the outer part of the sun itself. He perceives that the ever-changing coronal streamers indicate the vital energy of the sun, eNsn more strikingly than the flames which leap up over the sun's surface to tens of thousands of miles in height. The corona is as the bzsath of the great giant. If it could be watched, we might in a sense time the beatings of that mighty heart which pulsates light and Me and energy to all the worlds which circle around it.
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