Page:Proceedings of the Royal Society of London Vol 1.djvu/71

Rh phænomena from which he derives his inferences concerning the na- ture of the sun, Dr. Herschel proceeds next to treat of the regions of solar clouds The point he here principally insists upon, is, that the above-mentioned appearances are wholly incompatible with the hy- pothesis of the shining matter of the sun being a liquid, or an elastic fluid of an atmospheric nature; since, by the laws of hydrostatics, all the depréssions would be instantly filled up, and the elevations would as rapidly subside.. The opinion he advances is, that this shining matter exists in the manner of empyreal, luminous, or phos phoric clouds, residing in the higher regions of the solar atmosphere. Of these he assumes two different regions, or a double stratum of clouds, whereof the lower, viz. that which is nearést the sun, consists of clouds less bright than those of the upper stratum. The lower clouds are also more closely connected, while the upper ones are chiefly detached from each other, and permit us everywhere to see through them.

A number of additional observatións are here added; from which it is inferred, that the inferior clouds are opake, and probably not unlike those of our planet; and that their light is only the uniform refiection of the surrounding superior, ,self-luminous region. These lower clouds, it is thought, compose what the Doctor calls flats; and by a contrivance here described, he demonstrates, that the quantity of reflected light they transmit to us is to that of the superior and self-luminous clouds in the proportion of 469 to 1000

By the same process he proves also that, adhering to the same proportion, the quantity of light reflected by the solid body of the sun at the openings is represented by a number no greater than seven. Speaking of the planetary clouds, it is shown of what eminent service they must be to the whole solar system; since, by their means, nearly one half more light is transmitted to us from the sun than we should receive from the self-luminous stratum alone.

In a section on the solar atmosphere, after showing that its exist- ence cannot be denied,-since the clouds could not be kept suspended in the manner in which they are without an elastic atmospherical fluid to bear them up,-reasons are assigned why this atmosphere must be of a greater extent, of considerable density, transparent, and, like ours, subject to agitations by winds and other disturbing causes.

From these various observations and inferences is next derived a theoretical explanation of the solar phanomena; wherein the manner is described in which all the above-mentioned appearances on the surface of the sun are likely to be generated: after which follows an enumeration of the signs from which we may infer a deficiency or abundance of luminous matter in the sun. The former of these are a deficiency of empyreal clouds, of openings, and of ridges, nodules, and all that may be considered as prominences; whereas the oppo- site appearances are indications of increasing light and heat. The Doctor now does not scruple to assert that openings with great flats, ridges, nodules, and crankles, may induce us to expect a copious emission of heat, and therefore mild seasons; and that, on the con-