Tides are one of the most important factors to be taken into account by the coasting skipper. It is the rise and fall of the level of the sea at regular intervals, corresponding to the phases of the moon. That is so because the moon’s phases are an indication of her position in relation to the sun, and it is the combined gravitational attraction of those two bodies which raise the sea. The moon’s monthly (28-day) cycle gives the tides a fortnightly cycle, the tides being greatest when the sun and moon are either on opposite sides of the earth or on the same side, and least when they are at a right angle. The greatest tidal Ranges are called Spring tides, and arise at the new and full moon; the least are called Neaps and occur at the quarters. The fortnightly cycle of tides is rather convenient to live with: if High tide is around midday this week-end then it will be around midday in a fortnight’s time, but at morning and evening next week. The times of High and Low tides for each day of the year are shown in Tide tables, often free from chandler’s shops, but also in Almanacs and suchlike, Also shown are the Heights. (Please see also Tidal stream.)