You are used to seeing a sundial in the middle of a garden, and if you are like me, you look at the shadow, then compare the time to a wrist-borne chronometer, and note that the sundial is off by however many minutes. In _Sundials: History, Art, People, Science_ by Mark Lennox-Boyd I learned that this is at least doubly wrong. The author quotes Hilaire Belloc: "I am a sundial and I make a botch / Of what is done much better by a watch." He complements the wit of the couplet, and shows the errors. Firstly, he points out, sundials tell time perfectly well; they simply measure time differently than watches do, but neither of them is objectively "right". Secondly, sundials are not merely garden ornaments, and only one in this profusely illustrated and colorful book is from that category. The dials shown here are often scientific instruments and elaborate works of art that sometimes do not look like sundials at all. Not only are many styles of sundial illustrated here, but the science and history of making them is summarized; the reader will come away with a much better idea of how the solar system runs from the contemplation of these not-so-humble instruments.
Lennox-Boyd (or actually Sir Mark, since he has been, besides a Patron of the British Sundial Society, a Member of Parliament and a Foreign Office Minister), says that the association of the dial with the garden began in the Renaissance, not because the dials were ornaments, but because teachers of the time often used the garden as a place where lessons of science could be delivered. There are pictures here of artwork and architecture that one would not expect to be sundials at all. The Sundial Bridge across the Sacramento River in California is a suspension bridge, suspended on one side of the river from a huge, slanted support. The support just happens to be slanted at the correct angle to make it a gnomon, and its huge shadow sweeps along the ground beneath. The huge sundial at Jaipur in India has a gnomon that is big enough to walk up, fifty steep stairs. A Dutchman has designed beer glasses that you turn until the sunbeam through a circle on one side of the glass hits the date line on the other side; you can then tell if the time is after 5 p.m., the time when the inventor says the glass ought to be filled. There is a picture of a spherical sundial invented by Thomas Jefferson. The Disney World offices in Florida are "entertainment architecture", and part of the fun is that a central room is shaped like a truncated cone and has gigantic sundials visible on the outside and the inside, with quotations about time on marble plaques from such notables as Albert Einstein and Donald Duck. Sir Mark himself designs sundials, some of which are shown here. The most ambitious is one in Oliveto, Italy, within the stair tower of a house; a system of mirrors sends a sunbeam during different times of the day to different walls of the stairwell, each intricately crisscrossed with lines to read time, date, times of sunrise and sunset, and more.
Sir Mark points out that since we now have clocks accurate to more than one second in fifteen million years, sundials ought to be obsolete, but they are not. There has been a resurgence of interest in them, both in the historical forms and the modern ones which come in strange and undial-like shapes. "There is a particular symbolism in an object that does something helpful but requires no power and performs indefinitely," he writes. He is clearly fascinated with his subject, and this lovely and colorful book conveys the fascination perfectly.