Sundials - World's Oldest Clocks

North American Sundial Society

In 1636 or 1637 Samuel Foster, a distinguished Professor of astronomy at Gresham College produced a manuscript that describes the construction and use of an analemmatic sundial, a vertical sundial, and a declining sundial. 

The collection of 12 pages on four double leafs each measure 15 x 18 cm.  This manuscript relates to Samuel Foster's most important invention, a computational device known as a dialling scale, and precedes the publication of his second and most significant book in 1638 "The Art of Dialling: by a New, Easie, and Most Speedy Way ..."

The manuscript goes on auction by Voyager Press, an exhibitor at the Chelsea Antiquarian Book Fair at Old Town Hall, King's Road, London (51° 29' 14.9"N 0° 10' 07.3"W) on Friday Nov 7th and Saturday Nov 8th 2014. Foster's manuscript is available at a starting price of £4500.00

The Chelsea advertisment states, "Foster's manuscript writings are exceedingly rare with the latest manuscript appearing at Sotheby's Macclesfield sale in 2004. Four of Foster's treatises on dialling are bound in an eclectic volume of tracts by numerous authors which is held in the Emmanuel College library."

As described by the Chelsea auction, "In 1638 Foster wrote 'The Art of Dialling; by a New, Easie, and Most Speedy Way... how to describe the Houre-lines upon all sorts of Plaines, Howsoever, or in what Latitude soever Situated...' which was printed in London by I. Dawson for F. Eglesfield (sold at the signe of the Marigold in Pauls Church-yard). This work described the construction of horizontal, vertical and inclining sundials using his dialing scale, the first circular nomogram. In his appendix, 'shewing a ready way to find out the latitude of any place the Sunne... By the Meridian Altitude, and declination of the sun had; how to find the Latitude of the place, or the elevation of the Pole above the horizon', Foster recommended observing the altitude of the Sun above the horizon at mid-day (i.e. its highest point), and supplied a table of correction factors for the Sun's position along the ecliptic on every day of the year. He concluded the appendix with a worked example."

But the North American Sundial Society has a wonderful opportunity for you to obtain a Samuel Foster document for a fraction of the manuscript cost! ...

No, NASS does not have a copy of any of Samual Foster's manuscripts.  But it does have a copy of Foster's most significant book "The Art of Dialling" and through LuLu books, you can have a personal copy for only $18.  To order, go to: Lulu Books - Foster The Art of Dialling-1638

Samuel Foster’s "The Art of Dialling" is particularly noteworthy for two reasons. First, it contains the first appearance of dialing scales. For over two centuries following Foster, the latitude and hour scales he introduces in this book were recognized as providing the simplest means for laying out hour lines. Although George Serle was probably the first to put the scales on a ruler, he himself clearly attributes their invention to Foster. Second, it includes an interesting approach to drawing a dial on an arbitrary plane: Foster demonstrates how any plane can be treated as though it were the special case of a direct east - west plane, and then he completely solves the special case. This book consists of a facsimile reprint of the 1638 edition of The Art of Dialling. It also includes the full text of the 1675 edition produced by Leybourn and a paragraph by paragraph comparison of the two.

Now we have even a better deal for dialing.  Go to this website's Features/Sundials for Starters and read the article on Sundial Latitude to learn how to use George Serle's Ruler to determine the properties of an existing sundial or to create a dial of your own.   And at the bottom of the Sundials for Starters article, we provide a download photo of Serle's Ruler so you can draw (decline) your own sundial. Or, you can copy this photo:

Serle's Ruler based on Samuel Foster's Innovation