The Nebular Hypothesis.

Otago Witness, Issue 1598, 8 July 1882, Page 28

The Nebular Hypothesis.

Astronomers have noted among several other points of agreement, 'that all of the planets, as far as known, revolve about their axis, like the sun itself about its axis, from west to east ; that the planets themselves revolve about the sun from west to .east; that the 'satellites of the planets, revolve about their respective primaries from west to east, and have. also, as far as known, a motion on their axia from west to east ; that all of the planets revolve about the sun in the plane of the sun's equator, and that the satellites of the various planets revolve about their primaries in the plane of the equator of their respective primaries. , - Such an agreement of phenomena among' 236 heavenly bodies comprising our solar system cWld not be the result of chance,' and must, it was thought, be the effect of 'simple laws. To coordinate all of these different facts, tho 'nebular hypothesis' was advanced by La Place, i

In the first place it was assumed that in the original state the matter of which the solar system is composed existed in the form of luminous, incandescent matter, filling a space far greater than that now occupied by the system of which our sun is the centre. At first this vast amount of incandescent material formed.a homogeneous atmosphere, as it were, reaching out into space far beyond the orbit of the most distant planet of our system. But it had a motion abput a central point now oocupied by the sun, so that gradually the in-candescent-material was forced by simple natural laws to take the shape of an oblate ■spheroid, revolving in the plane of its longest diameter, or equator. In the process of contraction or aggregation of the' matter toward the common centre, large rings were broken from the moving mass. , Thesej 'acc6rding to well-known laws, would be flung off at the point where motion is the greatest, which would be at the point whera .the longest diameter of the ellipsis meets ' the surface. Successive contractions arid separations of matter would form the different , planets at different distances ' from the ' centre,' and as theyjwere all flung off from the point of greatest motion they would all be in the 'same plane as that of the Equator of the' central body. The motion around the central body, would, of course, be the same as that which th ! e particles had when forming a part of the homogeneous atmosphere, and the motions ' of' 'th& bodies about their respective axes wou|d be in the same direction, as is readily seen by .reference to the well-known laws of motion. So in the case of the planets themselves, bodies of matter thrown off, and now 'forming satellites, would he thrown off in the' plane of the equator of their respective planets, and would have the same motion about their axis as their primaries. By this simple hypothesis hiore'than 700 different phenomena are explained. But there are three apparent contradictions— namely, in the case of the inner satellite of Mars, which revolves from east to west about its planet • and in the caso of Uranus and Neptune, which' are thought to have motions on their, axis from east to west. Different theories have been advanced to account for these apparent contradictions, and in the case of the two outer planets explanations are accepted as satisfactory. In the case of the satellite of Mars, the explanation, is more difficult. But these are the only apparent contradictions to the theory and two of these are satisfactorily explained by the manner in which tho original material was thrown off from the central- mass. But '(the ready explanation of all but three or four of the phenomena of our solar system by tho ' nebular hypothesis ' renders it probable that this is the correct view to tak;e regarding tho genesis of the sun and sistecplanets.?, But for many years it seemed that this 'theory would be exploded, as it was impossible to find any nebulous matter in space. As telescopes of greater power were made, those luminous masses in the heavens that were thought to be nebulae, were resolved into stars. It was not until 1564, that true nebulous matter was dis covered, and then not by the telescope, but by spectrum analysis. The spectrum of incandescent solids give a continuous spectrum while that of incandescent gas gives a spec trum with, bright lines, which differ in position, according to the material of which the gas is formed. The spectrum of the sun has black lines, showing that the light from a luminous solid is shining through an atmosphere of luminous gas. . By means of the spectrum, there have been found in the heavens luminous masses which show bright lines when the light is analysed, proving rConclusively that the body from which such light proceeds is gaseous and not sohd. Thus true . nebulous matter has been found ; and more than this, m the nebula of Orion, the process of world formation is now going on before our eyes.~t Lecture by Professor Le Conte.

Artificial Porcelain. A process for making a new- kind which resembles porcelain, wifck* -°* ware sity.of baking the clay. H- 1 • ioXx^ the neces' Dr R: MartlU. ' c "J -"f bcou invented by The ae*- ' in Thuringia.

«ot soereat as that of the genuine porcelain, nor does it resist the dissolving action of water so well ; but it is cheaper, and the objects made from it, such as vases, dolls-heads, &c, are highly ornamental. Dreams and their Conditions/ Dreams; are night, thoughts, unchecked by (the judgment and uncontrolled by the will. It js not true that we do not reason in dreams, that the, exercise of the judgment is wholly suspended and that the will is entirely powerless or ceases to act. ' These faculties are not altogether 'in abeyance, but they doze while the subordinate powers of the mind— those which play the parts of picture carriers and record finders— ransack the treasures of memory and mingle together, ■hr the direst confusion, old things and new.Mmagination is not active, but it remains just enough awake to supply tlie connecting links which give seeming continuity to those" parts of the phantasmagoria which we chance-to remember on recovering perfect scltconsciousriess'; and which, being remembered, we call 'dreams.' /No one remembers more than one dream,- unless he has roused from Bleep more than once. This experience has lea to the inference that dreams only occur at the moment or in the act of awaking. There are dreams which take place in the process of returning to consciouspess-for example thoße instantaneous scenes an 4 spectacles which are Suggested by the sounder feeling that rouses thedreamer : but,-in result of a long and close study of the-subjectwith a view to discover tbe nature of dtfeamsand the laws of dreaming, fo^medical purppses, in connection with the treatments sleeplessness, I am persuaded that dreams occur in the course of sleep and are v "vholly forgotten. ' , Ifc That they do not and cannot take place m yßfeep sleep is probable, because deep sleep is H?eneral sleep, and whon this state prevails the subordinate faculties are sleeping, and the pictures and records which compose dreams are not disturbed. To understand dreams we must understand sleep, arid it is because the .two phenomena have not hitherto been studied together that so little is generally known about either.— Popular Science Monthly.