Sundials (dials) are known from at least 600 B.C. Egypt and China and 500 B.C. Greece. There are over a dozen different, formally designated types of sundials but they are typically circular, oblong or rectangular in shape, made of wood, ivory, silver or brass and marked to indicate time. All are fitted with a gnomon or vertical shadow-casting protrusion, which, on some types, is simply a thin string. They were sized to either mount on a table or pedestal or carry in the pocket. Some are constructed to be oriented with the disk horizontal, others vertical and still others inclined. Compasses were fitted to sundials during the late 1200s A.D. and a great number were made during the 1600s and 1700s. They were used to adjust clocks and pocket watches as well as to tell time themselves. They continued to be popular as pocket watch size instruments for calibrating watches until the mid-1800s when the widespread and accurate clocks of telegraph companies made sundials largely obsolete.The dipleidoscope, a sophisticated type of dial, was invented in 1843 by Edward Dent. By marking the meridian passage of the sun using a prism, compass and magnifying lens, the instrument determines time to within a few seconds of accuracy. The nocturnal is a related devise popularized in the early 1500s. It is used to find time at night with reference to the circumpolar stars. The nocturnal was used well into the 1700s and revived during the World Wars as a celluloid version called a ‘star clock’ as backup for military troops.