The mean longitude of the perigee, at noon, January 1, 180], was 279° 30' 5"-0. It has a real yearly increase of 11"-8, which, with the precession of the equinoxes, makes an increase of longitude of 61"-9.
The appearance of the sun is simply that of a ball of intense light, such as the human eye cannot bear,unless a hazy atmosphere or a dark glass be used as a screen. This light is so strong, that the brightest flames which human art can produce, when held before the sun, disappear, and ignited solids become dark spots. " The ball of ignited quicklime," says Sir J. Herschel, "in Lieut. Drummond's oxy-hydrogen lamp, gives the nearest imitation of the solar splendour which has yet been produced. The appearance of this against the sun was however, as described," merely a dark spot, " in an imperfect trial at which I was present. The experiment ought to be repeated under favourable circumstances." A very small portion of the rays collected into one spot [Bunsixe-GLAsses] is sufficient to melt metals. On examining the face of the sun with a telescope (of course with a dark glass before the eye), two circumstances are observed. The disc is not uniformly bright. " The ground is finely mottled," to use the words of the observer just quoted, "with an appearance of minute dark dots, or pores, which, when attentively watched, aro found to bo in a constant state of change. There is nothing which represents so faithfully this appearance as the slew subsidence of some flocculent chemical pro cipitates in a transparent fluid, when viewed perpendicularly from above ; so faithfully, indeed, that it is hardly possible not to be impressed with the idea of a luminous medium intermixed, but not confounded, with a transparent and unluminous atmosphere, either floating, as clouds in our air, or pervading it in vast sheets and columns like flame, or the streamers of our northern lights." The mind is lost in wonder at the idea of such a body of luminous material; but it is important to remember that living, as we must, under an atmosphere, we cannot positively assert anything as to what may take place beyond it. It is possible, though not very probable, that we should neither feel sensible of light nor heat, if we could meet the sun's rays before they have entered the air.
The other circumstance which is noticed on the sun's disc is the existence of black spots, by the regular motion of which the rotation of the body on its axis has been determined. These spots are of various irregular shapes, and are always surrounded by a border or penumbra, not so dark as the spot. They are of various sizes, from the least visible to the twentieth part of the sun in diameter. In
their neighbourhood are frequently observed streaks on the disc more luminous than the rest, called/ace/a', in which streaks spots frequently begin their appearance. The spots themselves alter in size, and gradually vanish, lasting various times, from a few days to six or seven weeks; ; the borders approaching each other in a manner which calcu lation shows must answer to hundreds of miles a day. Various theories have been invented to account for them, but none which has any appearance of probability except that of W. Herschel (` Phil. Trans.,' I SOD. He supposes that the sun has an atmosphere of greater density and depth than that of the earth ; and that above this atmosphere, or else mixed with the higher strata of it, is another atmosphere of eel f luminous clouds, of very variable depth, sometimes showing the lower atmosphere uncovered, which last reflects the light of the luminous atmosphere above it. A spot on the sun is a portion of the body of the sun itself, laid bare by some commotion which removes both atmo spheres, or the greater portion of them ; the penumbra round the spot, its never-failing attendant, arise; from the ridges of the lower atino ephere, which form the banks of the opening. The faculas, and general mottled appearance of the sun, arise from the luminous atmosphere having waves or ridges. From some measures of the light of different parts of the sun, Herschel thought that the non-luminous atmosphere reflects a little less than one-half the light it receives from the luminous atmosphere, and the solid body of the sun leas than one tenth. He also supposed that the presenee of spots and other disturbances indicated a large formation of heat and light in the sun, and was a prognostic of hot weather and fine seasons. This lie imagined he had verified by such comparisons as existed of the state of the sun at different times with the pries* of wheat immediately following: he found that, as far as his data, went (and he gives a proper warning as to their insufficiency), the price of wheat always rose when the sun was without spots, and fell when they }icon to reappear. We have not heard of any extensive attempt to verify or refute this theory; but No far as the hypothesis of the two atmoxplieres is concerned, it is one of high probability : we could hardly ask for a likely result of such a combination which does not actually make its Appearance. If it be correct, the son may very possibly be a globe habitable by living beings, perpetually illuminated by its upper atmosphere, the lower atmosphere preventing too much of either light or heat from reaching them.