The spring tides {13b} do not take place on the very day of the new and full moon, nor the neap tides on the very day of the quadratures, but a day or two after; the effect is neither greatest nor least when the immediate influence of the cause is greatest or least: as the greatest heat, for example, is not on the solstitial day, when the immediate action of the sun is greatest, but some time after it.—And although the action of the sun and moon were to cease, yet the ocean would continue to ebb and flow for some time, as its waves continue in violent motion for some time after a storm. {14a} Sir Isaac Newton has shown that the tides increase as the cube of the distances decrease, so that the moon, at half her present distance, would produce a tide eight times greater. Now the moon describes an ellipse about the earth, and of course must be once in every revolution nearer the earth than in any other part of her orbit; consequently she must produce a much higher tide when in this point of her orbit than in the opposite point. {14b} This is the reason that two great spring tides never take place immediately after each other; for if the moon be at her least distance at the time of new moon, she must be at her greatest distance at the time of full moon, having performed half a revolution in the intervening time; and, therefore, the spring tide at the full will be much less than at the preceding change. For the same reason, if a great spring tide happens at the time of full moon, the tide at the following change will be less. {14c} The spring tides are highest and the neap tides lowest about the beginning of the year; for the earth being nearest the sun about the first of January, must be more strongly attracted by that body than at any other time of the year: hence the spring tides which happen about that time, will be greater than at any other time, and should the moon be new or full in that part of her orbit, which is nearest to the earth at the same time, the tides will be considerably higher than at any other time of the year.