4 inch Square Hardboard Desk Clock  $24.99

Choose from Gold or Black Hands

Comes with Stand

Requires 1 AA Battey

Square Ceramic Tile Clocks

Choose from Gold or Black Hands

Requires 1 AA Battery

Stand not included

Available in

4 inch $19.99

6 inch $34.99

8 inch $44.99

To make the best of your Tide Clock, you should understand a little about what causes the high and low tides. The moon is the major cause of tides. The "lunar day" ( the time it takes for the moon to reappear at the same place in the sky) is 24 hours and 50 minutes. Most places have two high tides and two low tides each day. Therefore your Tide Clock has been designed so that it hand rotates once every 12 hours and 25 minutes ( twice each lunar day). Your Tide Clock always stays in exact step with the moon. But there are many other factors that can make the day-to-day tides a little earlier or later that the Tide Clock shows. It is the user's responsibility to determine these conditions for your own locality and to take them into account. The sun also affects the tides, but has less than half the influence of the moon. When the sun, moon and earth are lined up, as they are at the time of new moon and full moon, their influences combine and high tide is higher than normal and low tide is lower than normal. Also, at these times the sun will make the tides somewhat earlier or later than average. This is so important to set your Tide Clock on the day of the full moon, as the moon has the dominating effect with the tide.  

There are actually two tidal cycles; a twice daily cycle and a once daily cycle. On a tide when the two cycles help each other, high tides will be higher and low tide will be lower. On the next tide, when they conflict, the tidal range will be smaller. The relative strength of these two cycles varies from week to week, and also varies from one place to another. Along the Atlantic Coast the two daily tides have a similar range, but on the northern Pacific Coast there tends to be a larger difference between the two daily tides. Farther south in the Gulf of Mexico, the difference is so great there often appears to be just one high tide and one low tide per day. Abnormal atmospheric pressure can temporarily affect the time and height of tides. A difference of one inch in barometric pressure will cause about one foot difference in sea level. Both of these effects will change the times of low and high tides as well. The changing volume of the river flow will affect tides in the lower portions of rivers. 

For further information, we recommend the excellent discussion of tides in Chapman Piloting, Seamanship and Small Boat Handling, published by Hearst Marine Books, New York. This book is widely owned by boatmen and should be available in any library or bookstore near the coasts.