arranged around a great central aggregation (taking one of the earlier stages) could otherwise change than by aggregating towards their centre, unless we admit motions of revolution (in orbits more or less eccentric) the continuance of which would necessarily lead, through collisions, to the rapid growth of the central aggregation, and to the formation and slower growth of subordinate gatherings.

I have shown elsewhere how the formation of our solar system, in the manner supposed, would explain what Laplace admitted that he could not explain by his theory, -the peculiar arrangement of the masses forming the solar system. The laws of dynamics tell us, that no matter what the original configuration or motion of the masses, probably gaseous, forming the nebula, the motions of these masses would have greater and greater velocity the nearer the masses were to the central aggregation each distance indicating certain limits between which th velocities must inevitably lie. For example, in our sola system, supposing the central sun had already attaine very nearly his full growth as respects quantity of matte then the velocity of any mass whatever belonging to th system, would at Jupiter's distance be less than twelv miles per second, whereas at the distance of the earth, th largest planet travelling inside the orbit of Jupiter, t limit of the velocity would be more than twice as grea Hence we can see with what comparative difficulty aggregation would form close to the central one, and ho

where the quantity of matter was still great but the average velocity of motion not too great. Such an aggregation once formed, the next important aggregation would necessarily lie far outside, for within the first there would now be two disturbing influences preventing the apid growth of these aggregations. The third and fourth would be outside the second. Between the first aggregation and the sun only small planets, like the Earth and Venus, Mars, Mercury, and the asteroids, could form; and we should expect to find that the largest of the four small planets would be in the middle of the space belonging to the family, (as Venus and the Earth are actually placed), ile the much smaller planets Mercury and Mars travel bert on either side, one close to the Sun and the other ext to Jupiter, the asteroids indicating the region where the combined disturbing influences of Jupiter and the Sun prevented any single planet from being developed.

But I should require much more time than is now at 7 command to present adequately the reasoning on ich the theory of accretion is based. And we are not cerned here to inquire whether this theory, or Laplace's ry of contraction, or (which I hold to be altogether

probable than either) a theory involving combined cesses of accretion and contraction, be the true thesis of the evolution of the solar system. Let it Ese that we recognise as one of the earliest stages of

earth's history, her condition as a rotating mass of ng vapour, capturing then as now, but far more try then than now, masses of matter which approac...ei

near enough, and growing by these continual indraughts from without. From the very beginning, as it would seem, the earth grew in this way. This firm earth on which we live represents an aggregation of matter not from one portion of space, but from all space. All that is upon and within the earth, all vegetable forms and all animal forms, our bodies, our brains, are formed of materials which have been drawn in from those depths of space surrounding us on all sides. This hand that I am now raising contains particles which have travelled hither from regions far away amid the northern and southern constellations, particles drawn in towards the earth by processes continuing millions of millions of ages, until after multitudinous changes the chapter of accidents has so combined them, and so distributed them in plants and animals, that after coming to form portions of my food they are here present before you. Passing from the mere illustration of the thought, is not the thought itself striking and suggestive, that not only the earth on which we move, but everything we see or touch, and every particle in body and brain, has sped during countless ages through the immensity of space?

The great mass of glowing gas which formed our earth in the earliest stage of its history was undergoing two noteworthy processes,-first, the process of cooling by which the mass was eventually to become at least partially solid, and secondly a process of growth due to the gathering in of meteoric and cometic matter. As respects the

tion, I must remark that many astronomers appear to nie to give far less consideration to the inferences certainly deducible from recent discoveries than the importance of these discoveries would fairly warrant. It is now absolutely certain that hour by hour, day by day, and year by year, the earth is gathering in matter from without. On the most moderate assumption as to the average weight of meteors and shooting stars, the earth must increase each year in mass by many thousands of tons. And when we consider the enormous, one may almost say the awful time-intervals which have elapsed since the earth was in a gaseous condition, we cannot but perceive that the process of accretion now going on indicates the existence of only the merest residue of matter (ungathered) compared with that which at the beginning of those time-intervals was freely moving around the central aggregation. The process of accretion which now does not sensibly increase the earth's mass was then a process of actual growth. Jupiter and Saturn might then no longer be gathering in matter appreciably increasing their mass, although the quantity of matter gathered in by them must have been far larger than all that the other forming earth could gather in equal times. For those planets were then as now so massive that any possible increment from without was as nothing compared with the mass they had already attained. We have to throw back into yet more awful time-depths the birth and growth of those giant orbs. And even those depths of time are as nothing compared with the intervals which have elapsed since the

near enough, and growing by these continual indraughts from without. From the very beginning, as it would seem, the earth grew in this way. This firm earth on which we live represents an aggregation of matter not from one portion of space, but from all space. All that is upon and within the earth, all vegetable forms and all animal forms, our bodies, our brains, are formed of materials which have been drawn in from those depths of space surrounding us on all sides. This hand that I am now raising contains particles which have travelled hither from regions far away amid the northern and southern constellations, particles drawn in towards the earth by processes continuing millions of millions of ages, until after multitudinous changes the chapter of accidents has so combined them, and so distributed them in plants and animals, that after coming to form portions of my food they are here present before you. Passing from the mere illustration of the thought, is not the thought itself striking and suggestive, that not only the earth on which we move, but everything we see or touch, and every particle in body and brain, has sped during countless ages through the immensity of space?

The great mass of glowing gas which formed our earth in the earliest stage of its history was undergoing two noteworthy processes,-first, the process of cooling by which the mass was eventually to become at least partially solid, and secondly a process of growth due to the gathering in of meteoric and cometic matter. As respects the