| "I am a sundial, and I make a botch | | | | need to know both the latitude and longditude of its |
| Of what is done far better by a watch" | | | | location. For the United States and the United |
| So wrote Hilaire Belloc, but is this really fair? Sundials | | | | Kingdom this site can provide the information. The |
| are the earliest known form of time-keeping having | | | | gnomon should be set at the angle in degrees which |
| been used for some five thousand years. The Greek | | | | is equal to the latitude of your location. The sundial |
| historian Herodotus stated that sundials were first | | | | can then be fixed with the gnomon pointing to the |
| used by the Chaldeans and Sumerians in Babylonia | | | | Pole Star. There are various ways of achieving this, |
| which was part of the modern Iraq. They used | | | | the easiest of which, is to use a compass adjusted |
| vertical rods on their buildings and noted the position | | | | for the magnetic variation. Further details are beyond |
| of the shadow to record the passing of the hours. | | | | the scope of this article, but for those interested |
| The concept was developed by the Greeks and | | | | look at this site. |
| Romans who constructed various different shapes of | | | | If you have read this far you will have discovered |
| dial to enable them to tell the time and the season of | | | | that there is a great deal more to the sundial than a |
| the year. Usually these were bowl-shaped dials with | | | | mere item of garden decoration. If this has piqued |
| vertical or horizontal gnomons (shadow-casters) and | | | | your interest in the subject, then you are not alone. |
| hour lines marked in the hollow of the bowl. Over the | | | | There are Sundial Societies in countries around the |
| years more elaborate designs were produced until | | | | world. The North American Sundial Society has details |
| the advent of accurate clocks when the function of | | | | of its objects and activities on its website. |
| the sundial became more decorative than as a reliable | | | | A number of sundial trails have been established. A |
| means of telling the time. | | | | good example is the Thames Sundial Trail in London, |
| The question is often asked "Can a sundial really tell | | | | England. This site lists a number of other trails in |
| the correct time?" to which you will receive the Alice | | | | countries all over the world but only two in the |
| in Wonderland reply that it depends upon what you | | | | United States. However the North American Sundial |
| mean by "the correct time". Our clocks and watches | | | | Society has a complete list on its website. |
| work on the basis of there being exactly | | | | Two rather different designs are shown here. The |
| twenty-four hours between one day and the next | | | | first, which is commonly referred to as a Human |
| but, because of the eliptical nature of the earth's | | | | Sundial, uses the person's shadow to indicate the |
| orbit around the sun, the time shown on the sundial | | | | time. By standing in the appropriate box for the date |
| will vary according to the seasons. In February by | | | | the shadow will show the correct time. The second is |
| the clock the sun is almost fifteen minutes slow, | | | | a Digital Sundial which sounds like a contradiction in |
| whereas during the spring and summer months it | | | | terms but in reality is just a rather clever design. |
| gains and loses between four and six minutes in two | | | | Many sundials have a motto inscribed on the face. |
| cycles. At the other extreme in November the sundial | | | | Often these are rather serious in tone and of the |
| appears to be some seventeen minutes fast. In fact | | | | "Tempus fugit" variety but you also find some |
| the sundial is accurate on only four days of the year, | | | | written in a lighter vein. Here are a few of my |
| about April 15, June 14, September 2 and December | | | | favourites: |
| 25. Some sundials include a table showing the | | | | The shadow of my finger cast |
| deviation from "clock time" according to the date. | | | | Divides the future from the past |
| The time indicated by the sun will also vary with the | | | | The clock the time may wrongly tell, |
| location of the dial. The sun travels across the sky at | | | | I never if the sun shines well |
| the rate of fifteen degrees per hour so every | | | | I stand amid the summer flowers |
| degree of longditude represents a difference of four | | | | To tell the passage of the hours |
| minutes from the standard meridian for the region. | | | | And finally again from Hilaire Belloc: |
| The angle of the gnomon also depends on the | | | | I am a sundial, turned the wrong way round. |
| situation, so to set up your sundial correctly you | | | | I cost my foolish mistress fifty pounds! |