From a consideration of the causes of earthquakes the author is led by his accustomed train of thought to draw the ethical lessons which the subject suggested to him. He repeats his belief that against the perils of earthquakes, as against all the other dangers and fears of life, the only assurance is to be obtained from elevating studies and a contemplation of nature (265). It matters not when or in what form we shall quit life, whether from some trifle or from a world-wide catastrophe. To be happy without fear of anything that may befall us, we must carry our life in our hands, steeling ourselves against fear, and prepared even to welcome death as the advent of a friend. BOOK VII After a brief introduction, marked by no little elegance and literary skill, the author introduces the subject of the heavenly bodies, and more especially of Comets which he is to discuss in this Book. He proposes at the outset to endeavour to ascertain whether the earth stands still while the universe revolves round it, or if it is the universe that remains at rest while the earth revolves. But he is led on from one topic to another, without having arrived at a definite solution of this problem when the volume comes to an end. From various expressions, however, it may be inferred that he adhered to the primitive belief that it is the universe which goes round the earth. Thus in Chapter IX. he speaks of the movement that drags the universe along and asks what is swifter than that revolution (281). The heavenly bodies may not stand or turn aside, they all move onward with the irrevocable movement of this eternal creation (299).