61. =Globular Form of the Earth and the Heavenly Bodies.=--It is supposed that the sun, moon, earth, and all the heavenly bodies were once in a liquid state, and that they owe their globular shape to this fact. As they whirled on in this condition in their course, the different solids were gradually formed, and at length they acquired their present state. How all the mighty changes could be effected in our earth, converging it from a liquid into a body with a solid crust, having such various substances in it, and so variously arranged, with its depressions containing water, and the whole covered with its robe of air fifty miles in thickness, we can not understand. And yet there are some portions of the process which chemistry and geology have revealed to us, giving us some glimpses of the wonders which, during the lapse of ages, God wrought in our earth in preparing it for the habitation of man. [Illustration: Fig. 11. Fig. 12.] 62. =Crystallization.=--The arrangement of the particles of solid substances is different from that of liquids. The tendency here is to straight lines and angles; that is, to crystalline forms. Alum or common salt, when it becomes solid from a solution, forms crystals. So also does sugar. The crystals of different substances are different. In Fig. 11 you have the crystal of common salt, and in Fig. 12 that of alum. We see this crystalline tendency every where, even in the rude rocks and common stones. The rocks are disposed to exhibit regular layers, or columns, or battlements, and always do so except when interfering circumstances prevent. And when you examine their composition, or that of the stone under your feet, you see the same crystalline disposition in detail that you see in the mass. 63. =Crystallization of Water.=--Water, when it changes into a solid, shows the same disposition, of which the crystals of the snow and the frost-work on our windows are familiar examples. When snow forms, the water of the clouds is suddenly crystallized by the cold air, the particles taking their regular places more readily and certainly than if they were guided by intelligence, because in obedience to an unerring law established by the Creator. We sometimes have an example of this sudden crystallization of water under our eye. The water in a pitcher may remain fluid, although it is cooled down to the freezing point, and even below it, if it be kept perfectly still. But on taking up the pitcher the water at once becomes filled with a net-work of ice-crystals. The explanation is this: The stillness of the water has prevented its particles from taking on the new arrangement needed for the formation of ice; but the jostling of them in taking up the pitcher has served to make them do it thus suddenly. [Illustration: Fig. 13.]