SUNDIAL SECTIONS:

Sundials Home

History of Sundials

Why the Sun Dial keeps time

Developing and Making Sundials

Sundial Materials

Sundial Hour Lines Lay out

Sundial "Furniture"

Declination Lines of Sundials

Portable Sundials

Interesting Sundials of the World

HOW TO DESIGN AND MAKE A SUNDIAL - Page 5

Do not try to lay out the hour lines except in a general way. After the full size drawing has been brought to the point where you are ready for the hour lines, the next step is to lay out those lines, but before this can be accomplished the latitude of the place where the sundial is to be situated must be found, because the shape of the gnomon is dependent upon it. This can be done very simply as follows: Obtain, from a local stationer or book store, a copy of the topographic map for your locality. A portion of one is shown in Figure 17 facing page 43. They are published by the United States Geological Survey, and generally cost 15 cents at stationers and bookstores. If not obtainable there, they may be obtained from the Director, U.S. Geological Survey, Washington, D.C., at a cost of 10 cents. Latitude and longitude are shown in fine black lines on the map, at 5 minute intervals. The latitude may be obtained from the horizontal lines and the longitude from the vertical lines. The bottom and top lines are marked at either end with the degree and minute of latitude, and the intermediate lines are designated by minutes only, except where a change in the degree takes place in the middle of the sheet. The vertical lines of longitude are similarly marked. Now find your position on the map and make a cross as shown in illustration facing page 43. In the figure, the cross lies between the latitude of 42° 30' and 42° 35'; therefore we must find how far the cross is away from either parallel of latitude in order to find the latitude of the cross. This can be accomplished by using the line of longitude, AB, or by using a line which passes through the cross and perpendicular to the lines of latitude. In either case another line is drawn at random from A to C, as shown.

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