EPAULE, OR SHOULDER. In fortification, that part of a bastion adjacent to the junction of a face with a flank. The actual meeting of these two lines forms the "angle of the shoulder." EPAULEMENT. In fortification, a covering mass raised to protect from the fire of the enemy, but differing from a parapet in having no arrangement made for the convenient firing over it by defenders. It is usually adopted for side-passages to batteries and the like. EPAULET. The bullion or mark of distinction worn on the shoulders by officers, now common to many grades, but till recently worn only by captains and commanders, whence the brackish poet-- "Hail, magic power that fills an _epaulet_, No wonder hundreds for thee daily fret!" the meaning of which is now pointless. EPHEMERIS, OR NAUTICAL ALMANAC. This in its wide sense, and recognizing its value to navigators and astronomers, must be pronounced one of the most useful of publications. How Drake and Magellan got on is matter of marvel, for sailors were not especially administered to till 1675, when the _Kalendarium Nauticum_, by Henry Seaman, Mariner, appeared; it comprised the usual matter of annual almanacs, and was enriched with such precepts and rules in the practice of navigation and traffic as are in daily use. But in 1767 our nautical almanac, a tabular statement of the geocentric planetary positions, which may be said to have created a new era in voyaging, was published; and this book, with certain alterations, was in force up to 1830, when a commission of the Royal Society and astronomers established the present _Ephemeris_, now so much valued. It is published annually, but computed to four years in advance, to accommodate those proceeding on long voyages. Attempts have been made in other countries to publish _The Nautical Almanac_, improved and corrected, but they are mere copies, corrected by the errata furnished annually in advance. EPICYCLOID. A geometrical curve generated by making a circle roll upon the circumference of another circle; it is found useful in determining the figure of the teeth of wheel-work, and other purposes in mechanics. If the generating circle proceeds along the convexity of the periphery, it is called an upper or exterior epicycloid; if along the concavity, a lower or interior epicycloid. EPOCH. The time to which certain given numbers or quantities apply. EPROUVETTE. A small piece of ordnance specially fitted for testing the projectile force of samples of gunpowder. EQUATED ANOMALY. This is also called the true anomaly, and is the distance of the sun from the apogee, or a planet from its aphelion, seen from the sun. EQUATION, ANNUAL. _See_ ANNUAL EQUATION. EQUATION OF EQUINOXES. The difference between the mean and apparent places of the equinox. EQUATION OF THE CENTRE. The difference between the true and mean anomalies of a planet.