LUNAR THEORY. 540 LUNDGREN. happens at 54° 44' on each side of line of syzy- gies. It is negative more tluiu halfway round. The effect of this is to lessen the earth's at- traction for the moon by nearly 1/300 and to increase its mean distance. This makes the month about an hour longer than it would be otherwise. The diminution of the earth's attraction for the moon at apoyee (q.v.) and the reverse of this at perigee (q.v.) causes an oscillation of the line of apsides (q.v.). The disturbing force at apo- gee, however, predominates, and the line of apsides completes a revolution in about nine years. The tangential component retards and accel- erates the motion of the moon. This is the main cause of an inequality, called the variation. Its maximum amount is 3U' 30", and this is attained half-way between the syzygies and quadrature. The orthogonal component tends to draw the moon toward the ecliptic. This causes the in- equalitv known as the regression of the nodes (q.v. )." which complete a revolution in about nine years. This force vanishes twice a year when the sun is at the nodes of the moon's orbit, since then they are both in the same plane. Evection is another disturbance which puts the moon forward or backward in the orbit about 114°. It has a period of about 1% years, the time required by the sun to pass from the line of ajisides to the same line again. The cause of this inequality is the increase and decrease of the eccentricity in the moon's orbit, caused by the in- <rease and decrease in the earth's attraction on the moon. The annual equation is an inequality produced by an increase in the sun's disturbing force, when tile earth is nearer to the sun than its mean dis- tance. As a result of this the month is length- ened or shortened, depending upon whether the increased disturbing force aids or retards the motion of the moon. The secular acceleration of the moon's mean motion was discovered by Halley by comparing ancient and modern eclipses, and the moon is be- lieved to have gained in this way one degree dur- ing the Christian Era. Laplace (q.v.) explained this secular acceleration by the fact that the earth's orbit, under the action of other planets, is grow- ing less eccentric. As a result of this the aver- age disturbing force of the sun is diminished, and the month is shortened little by little. The pe- riod of this inequality is 25,000 years. Of these irregularities, evection is the only one ■which was known to the ancients. It may affect the time of an eclipse by nearly six hours, and was discovered by Hipparchus (B.C. 1.50) while observing an eclipse. The variation was discov- ered by Tycho Brahe. This does not affect the time of an eclipse, and therefore escaped the Greek astronomers. The inequalities mentioned above are only the principal ones. In the com- putation of nautical almanacs, about 70 are taken into consideration for determination of longitude, and half that number for latitude. See Moon. Consult Chauvenet. Ftpherlcal and Practi- cal Aslronom;/ (Philadelphia, 1863). LTJNATIC. In law, a person who was origi- nally possessed of a sound mind, but whose reason has become so clouded and deranged that he can- not be held legally accountable for his acts. Jlost authorities hold that a lunatic is one who has become entirely bereft of reason, and classify under various other terms the dill'erent phases of mental unsoundness which may inllucnce a per- son's legal relations. For example, iiiunotiiunia usually consists of an abnormal aversion to a single thing or person, and may be so violent as to pervert entirely the victim's judgment as to the object of his delusion, and this must be taken into account by the law; but such a person can hardly be called a lunatic if his other reason- ing faculties seem normal. A lunatic cannot be held for a criminal act, as he cannot distinguish between right and wrong; his contracts are void- able; he cannot make a valid disposition of his property by will, and he should be represented by a committee or guardian for all legal purposes. A lunatic may have a lucid interval (q.v.) dur- ing which he is legally competent. See Rcdjwld on. Wills; Ordronaux, jurisprudence of Medicine; also Lunacy. LUNATIC ASYLUM. See Insane Asylum. LUND, ISond. An episcopal city of Sweden, situated 5 miles from the Sound, 11 miles north- east of Malmii (Jlap: Sweden, E 9). Its cathe- dral, which is the largest and most beautiful Romanesque building in Scandinavia, dates from the twelfth century. Near it are the university buildings, including the historical museum. The university has faculties of theologj'. law, medicine, and ]ihilosophy; was founded in 1000, and is attended by some G50 students. The chief in- dustries of the town are sugar-refining and the manufacture of machinery. Population, in lliol, 16.021. In the Middle Ages Lund was long the largest city of Scandinavia. In the eleventh cen- tury it was the seat of a bishopric, which in 1104 was" erected into an archiepiscopal .see. The Arch- bishop of Lund claimed jurisdiction over all the sees of Scandinavia. Lund was often the resi- dence of the Danish kings. The town sulTered during the wars between Sweden and Denmark, and passed from the possession of the latter in 16.58. Here the treaty of peace was signed in 1679 by which Skane was permanently confirmed as a part of Sweden. LUND, lund, Troels Frederik (1840—). A Danish historian, born at Copenhagen. He was appointed professor at the Military School of Fredericksburg. His publications include an important work on Scandinavian history, Dan- marks og Xorges Historic i Slutningrn af det IGde Aarhundrede ("History of Denmark and Norway to the End of the Sixteenth Century") (1880-92). LUNDA, Inn'da. Bantu peoples living north of Lake Bangweolo, Britisli Central Africa. They are tall, well proportioned, with re.gular features, and a complexion lighter than among other tribes of the Bantus. They depend on agriculture and trade in ivory and slaves. They file the teeth, tattoo themselves, and smear the body with oil. All travelers agree that the Lunda are a mild, inoffensive people, remarkable in Africa for the deference they 'show to their women. LUNDGREN, loTmd'gren. Egron Sellif ( IS1.5- 75). A Swedish water-color painter. He was born at Stockholm. December IS. 3815. He studied at the Academy of Stockholm, and afterwards in Paris under Cogniet. He sojourned in Italy, 1841-49, devoting him.self to water-colors. From there he went to Spain and then to Eng-
