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of separate particles: attracting every particle, independently of the others. It is essential to bear this in mind. The next thing is, that it attracts every particle with a force which depends upon the distance of the attracted particle from that body which is the cause of attraction; and the nearer that body of the more strongly the particle is pulled by the attracting body. You will see then, that the sun attracts those, parts of the earth next to it with a greater force than those parts near the centre of the earth. At A, Figure 46, the sun's attraction is stronger than at C, and therefore the sun is always acting upon the part A nearest to it, as if it were pulling it away from the earth's centre. This is not merely because the whole force which the sun exerts upon A is directed towards S, because if the sun pulled the centre and the surface of the earth equally, it would not tend to separate them; but it is because it pulls the part at A more than it pulls the central part C, and thus it tends to pull it away from the centre of the earth