722 DAX he reorganized the schools of that province. In 1855 he was appointed principal and pro- fessor of natural history in the McGill univer- sity at Montreal, of which he has since become vice chancellor. He also organized and has managed for the past 16 years the Protestant normal school for the province of Quebec, and within the last three years he has established a school of practical science in his university. Dr. Dawson has the degree of LL. D. from McGill university, and is a fellow of the royal and geological societies of London, and a mem- ber of many other learned societies. DAX, a town of S. W. France, in the depart- ment of Landes, on the left bank of the Adour, 25 m. N. E. of Bayonne; pop. in 1866, 9,469. It is a principal station on the railway from Bordeaux to Bayonne. It is of ancient origin, with ditches and ramparts of Eoman construc- tion. The most remarkable building is the cathedral, built under Louis XIV. It has man- ufactories of liqueurs and delft, and some trade is carried on in grain, wine, timber, vegetables, wax, and honey ; and it is a considerable entre- pot of goods exported from France to Spain. Its chief attraction now is its hot mineral springs, whose temperature varies from 86 to 166 F. From these it was called by the Eomans Aquro Tarbellica3, afterward by the French Ville d'Acqs, and then simply Dax. DAY, the period of the earth's rotation on its axis. The distance of the first fixed stars is so great that their apparent positions are not affected by the motion of the earth in its orbit ; hence the time between the successive passages of a fixed star or any other equally fixed point of the heavens over a meridian is uniform, and is called a sidereal day. The point of the heav- ens usually employed is the vernal equinox, which, though not absolutely fixed, does not vary apparently during a single day. This day is only used by astronomers. In common life the day is measured by the return of the sun to the meridian, called the solar day. It varies from several causes, its average length being about four minutes greater than that of the sidereal day. The principal causes of variation are the motion of the earth in its orbit and its varying distance from the sun. The day according to which clocks and watches are regulated is the average of all the days in the year, and is called the mean solar day. The time of this day is called mean solar time, while the actual time by the sun on any given day is called apparent time. The difference between the two is the equation of time. They coincide four times in a year. Their maximum difference, occurring twice in a year, is about 16 minutes. Astronomers in measuring mean solar time suppose a fictitious sun moving uni- formly in the equator, and coming to the vernal equinox at the same instant with another fic- titious sun moving uniformly in the ecliptic, and coming to the perigee at the same instant with the real sun. The sidereal day is 23h. 56m. 4'09s. of mean solar time. Astronomers DAY begin the day at noon, and count the hours from 1 to 24. In most countries the civil day begins at midnight, and the hours are counted from 1 to 12 at noon, and thence from 1 to 12 at midnight. The word day is also used in opposition to night, to denote the time during which the sun is above the horizon. This va- ries with the latitude and the season of the year. As we go north it increases in summer and decreases in winter. At the equator the day is always a little more, and the night a little less than 12 hours. At the poles the day is a little more, the night a little less than six months. DAY, Jeremiah, president of Yale college, born in New Preston, Conn., Aug. 3, 1773, died in New Haven, Aug. 22, 1867. He entered Yale college in 1789, but on account of infirm health was not able to go on with the class; but after an absence of several years he resumed his studies, and graduated with high honor in 1795. He succeeded Dr. D wight in the charge of a school at Greenfield Hill, continued there a year, and was then elected tutor in Williams college, and in 1798 in Yale college. While acting as tutor he began to preach as a candidate for the ministry ; but in 1801 he was elected professor of mathematics and nat- ural philosophy in Yale college. His health being still feeble, he was not able to enter on his new duties till 1803, but after that con- tinued in them till 1817, when, on the death of Dr. Dwight, he was elected his successor as president. In July of the same year he was formally inaugurated, and on the same day was ordained as a minister of the gospel. In 1817 he received the degree of LL. D. from Middlebury college, and in 1818 that of D. D. from Union college, and the latter also from Harvard college in 1831. He continued in the presidency of Yale college till 1846, when he resigned on account of feeble health. His learning and talent, united with great kindness of heart, soundness of judgment, and urbanity of manner, secured alike the respect and love of his thousands of pupils. He was distinguished as a mathematician, and as a close and vigor- ous thinker. His mathematical works, which have passed through numerous editions, are "Algebra" (1814), "Mensuration of Super- ficies and Solids" (1814), "Plane Trigono- metry " (1815), and " Navigation and Survey- ing" (1817). He also published "An Inquiry on Self- Determining Power of the Will, or Contingent Volition" (1838; 2d ed., 1849), " An Examination of President Edwards's In- quiry as to the Freedom of the Will " (1841), and a number of occasional sermons, and con- tributed papers to the " American Journal of Science and Arts," the "New Englander," &c. An address commemorative of his life and ser- vices was delivered by President Woolsey, and published (1867). DAY, Stephen, the first printer in New Eng- land, born in England in 1611, died in Cam- bridge, Mass., Dec. 22, 1668. He came to
