THE POPULAE EDUCATOB. 



indication that the law of gravitation was imposed upon this 

 vapour, and it began to revolve round its centre of gravity, thus 

 collecting itself into a fire-cloud, whose outmost edge stretched 

 beyond the orbit of our most distant planet. A moment's 

 thought will decide that the shape it would take would be that 

 of a watch, providing that the edges were somewhat thinner. 



As this fire-cloud revolved in space, which is devoid of heat, 

 it would rapidly cool. Obedient to the great law, as it cooled 

 it would contract and become more dense, until its outward edge 

 had reached so low a temperature that it could no longer 

 remain in its vapour condition, when it would condense into a 

 liquid. 



The globe of red-hot matter thus produced has since lost all its 

 heat, and forms the furthest planet of our system. So one after 

 another the different planets condensed from the vapoury mass. 

 As might be expected, they did so at intervals, regulated by a law, 

 named, after its enunciator, "Bode's law." There are several 

 points in our system which support this theory. The planets and 

 their moons all move in the same direction. Their orbits are com- 

 prised in a narrow belt, which represents the thickness of the 

 cloud. The exterior planets are light, and have many moons 

 both which peculiarities arj accounted for by the fact that the 

 cloud would be denser near its centre, and gradually become 

 more rare towards its outward edge, in the region where these 

 planets condensed. There yet remains a further confirmation : 

 the existence of Saturn's ring and the asteroids. It is well 

 known that matter in rotation, if it be sufficiently pliable, will 

 assume one of two shapes either a sphere or a ring. The 

 sphere will not bo perfect, but will flatten at its poles and 

 bulge out at its equator in proportion to the rapidity of its 

 motion and the slight cohesion of its matter. The exterior 

 planets are so elliptical in their shape that, looking at them 

 through a telescope, the eye is at once struck with the fact. 



The earth's equatorial diameter is twenty-six miles longer 

 than its polar. It has been suggested that this shape may be 

 due to the denudation of the poles by the continued evaporation 

 of water in the regions of the tropics and its condensation as 

 rain at the polar regions. By this means a thickness of thirteen 

 miles was gradually transported from the poles, and deposited 

 at the equator. But if this were the case, the earth would still 

 possess a spherical nucleus. This, however, is disproved by 

 certain astronomical considerations concerning the motion of 

 the moon. Hence, the earth must be elliptical from its centre 

 that is, its shape is due to the action of its rotation when its 

 mass was pliable. 



The ring is the only other shape which fluid in revolution can 

 assume to be in equilibrium ; but it is remarkable that if a ring 

 of oil which collects round a wire shape, immersed in a spirit 

 of the same specific gravity as the oil, be made to revolve by 

 turning the wire, when a certain speed is attained the ring 

 suddenly breaks up into innumerable globules. 



The existence of the ring of Saturn proves that that planet 

 must once have been in a fluid condition. The asteroids seem 

 to have been a ring of much larger dimensions, which, as in the 

 instance quoted, broke up into many small planets. The view 

 with which they used to be regarded namely, that they were 

 fragments of a planet which some internal convulsion had 

 shattered is now abandoned ; for it can be proved that in this 

 case the fragments must periodically return to the point from 

 which they were hurled, which is not the case. 



In the lapse of untold ages the various members of our 

 system condensed from this vapour-cloud, and in process of time 

 cooled down, until, losing their heat, they ceased to be luminous, 

 and assumed the appearance with which we are familiar. 



The sun is the remnant of this cloud, which was the result of 

 the Great Being's first command, and no doubt the conden- 

 sation and contraction are still going on. 



But to return to our earth. After our globe had assumed the 

 liquid condition, the process of cooling would still proceed, and 

 the consequent contraction. The result of this would be that 

 the vast ball of molten matter would be covered with a solid crust 

 or skin. This crust, owing to the greater contraction of liquids 

 than solids, would wrinkle, and, seeing the earth possessed a 

 uniform motion, the wrinkles would take a uniform direction : 

 this direction was from north to south. Whether water was 

 existing in the atmosphere which enveloped the earth, as 

 highly rarefied steam or as its constituent gases, oxygen and 

 hydrogen, in an uncombined state, is a matter of little moment. 



For many ages the surface of the earth was too hot to permit 

 water to rest upon it ; but when the cooling had sufficiently pro- 

 ceeded to allow of this, then that vast quantity of fluid which 

 is the blood of the geological life of the world covered the 

 surface of hard bare rock from pole to pole. But for long ere 

 this was effected, the water, in a state of condensed vapour, 

 which forms clouds, must have enwrapped the earth, and the 

 operation ascribed to the second period of creation was the 

 making of a firmament which should divide the waters which 

 were above the earth the clouds from the waters which were 

 on the surface : meaning to say that the cooling had sufficiently 

 proceeded to allow the water to remain on the surface, and 

 clouds to form. 



With the dawn of the third era began the operation of a force 

 which still exists, and to which we shall frequently have to 

 allude : the heaving up, gradual and slow, of the northern 

 hemisphere, and the consequent draining off of the waters 

 towards the southern pole. The ridges, or the crests of the 

 wrinkles, which had a generally northern direction, being elevated 

 at their northern extremity, wquld form continents of a triangular 

 shape, the point of the triangle tending southwards. This ap- 

 pearance is still perpetuated in North and South America, 

 Africa, India, etc. A glance at the map of the world will 

 afford many confirmations of this theory ; making allowance for 

 the repeated elevations and immersions of the continents, which 

 would necessarily cause some alteration in their shapes. This 

 theory bears out the assertion of the sacred record, that the 

 sun was not made until the fourth day that is, Mercury and 

 Venus were not until then separated from the mass, and that 

 luminary which we call the sun produced as he now appears to us. 



From this time the various forces which are still existing date 

 the commencement of their operations. The tides, the ocean 

 currents, the rivers, the streams, the rain, the atmosphere, all 

 began their action on the Primary rocks, wearing them down, 

 and redistributing their particles in homogeneous order along 

 the ocean bed ; here forming stratified rocks which imbedded 

 the organic remains of that life which the Author of all life 

 had so abundantly shed upon the now habitable earth. Whether, 

 in after years, new facts discovered will cause another theory 

 to supersede this, remains to be seen. As yet, this is the only 

 supposition at all tenable. And now, leaving theory, it is our 

 duty to describe in turn these different agents, to notice their 

 present action, and to discover traces of their handiwork in the 

 rocky pages of Nature's book. 



LESSONS IN ARITHMETIC. XXXVI. 



SIMPLE INTEBEST (continued). 



9. Another method of finding the simple interest upon a given 

 sum for any assigned NUMBER OF DATS. 



Let it be required to find the interest on .300 17s. lOd. for 

 218 days, at 6 per cent, per annum. 



218 (Jays is fH of a year. 



Hence the answer would be given by simplifying the ex- 

 pression. 



218 

 365 



(30017s. lOd.) 



100 



In questions where the time given is a number of days, it is 

 manifest that the divisor 36500 will always occur. For a 

 reason which will be explained immediately, twice this number, 

 that is 73000, is a more convenient divisor, so that we must 

 double the numerator of the fraction. 



Now, 12 x 218 (.300 17s. lOd.) = ,787132 12s., so that 



.,787132 12s. 

 the result will be obtained from & 



The division by 73000 may be effected as follows : 

 It will be found that 1 + J + ^ + s&o : 



73000 



tV 24333J 

 2433J 

 243J 



100010 



Hence, if to any number we add a third of itself, then ^th of 

 that third, and again Jgth of this last quotient, we shall in faot 

 have multiplied it by the fraction V^. If then wo further 

 divide by 100010, we shall have divided the number by 73000. 



