77 



MALVOISINE, WILLIAM DE. 



MANBY, CAPTAIN GEORGE. 



78 



us tbe flame of a candle, Mains was for a time at a loss to divine the 

 cause ; but after making several observations on the light from the 

 same windows, he ascertained that the effect was produced only when 

 it fell on them at a particular angle of incidence, which he determined 

 from the known position of the sun with respect to the surface of the 

 building. 



In the prosecution of the researches to which this interesting dis- 

 covery gave rise, Mains found that when a pencil of light is reflected 

 from unquicksilvered glass at an angle of incidence equal to 54 35', 

 or from the surface of water at an angle equal to 52 44', the reflected 

 light possessed the same properties as were exhibited by one of the 

 pencils produced by double refraction in a crystal. He observed also 

 that when the pencil reflected from a transparent medium, at a certain 

 angle of incidence, is made to fall on another such medium at a certain 

 angle of incidence ; if the plane of the second reflection is coincident 

 with the plane of the first, the light is reflected as usual ; but if the 

 planes are at right angles to one another, no reflection takes place at 

 the second surface, the pencils of light being wholly refracted. 



To the effect produced on light so reflected, Malus gave the name 

 of polarisation ; conceiving that the particles of light have poles or 

 axes, and that, on entering the doubly refracting crystal, those which 

 form one of the pencils may arrange themselves so as to be capable of 

 being transmitted through it, while those which should have formed 

 the other ray may have such dispositions as prevent the passage, in 

 certain directions, from beiug effected. 



These phenomena may be said to have laid the foundation of a new 

 branch of physical optics ; and an account of them is given in the 

 ' ilemoires de la Socitito d'Arcueil,' as well as in the ' MiSmoires ' of 

 the French Institute. Of this learned body Malus was immediately 

 elected a member ; and, in 1811, though, on account of the war, there 

 was scarcely any intercourse between Great Britain and France, the 

 Royal Society of London awarded him the Rumford medal; thus 

 performing a noble act of homage to scientific merit in the person of 

 a foreigner, and one who carried arms among the enemies of the 

 country. 



In 1810 Malus published at Paris his 'Thdorie de la Double Refrac- 

 tion de la Lumieres dans les Substances ciistallisees ; ' and in the 

 following year he presented two papers to the Institute on some 

 remarkable phenomena of polarised light. In the first of these it is 

 shown that when a pencil, after being polarised by reflection, falls on 

 glass, part of it is reflected and part transmitted; the reflected part 

 is wholly polarised in one direction, while the transmitted part consists 

 of two portions, in one of which the particles preserve the character 

 of direct light, and in the other the light is polarised in a direction 

 contrary to that of the reflected pencil : it is added that the portion 

 which has the character of direct light diminishes gradually by 

 transmission through several plates of glass successively; and at 

 length the whole of the transmitted ray becomes polarised in a 

 direction contrary to that of the reflected pencil. In the second 

 paper it is shown that all polished bodies, opaque and trans- 

 parent, polarise light by reflection; and that, in different bodies, 

 the polarisation takes place with different angles of incidence. 

 Polished metals however resisted for a time the efforts of Halus to 

 produce the phenomena of polarised light ; but, at length, by a par- 

 ticular disposition of the reflecting surface, he succeeded in exhibiting 

 them : he discovered that the pencils reflected from polished metals 

 are polarised in opposite directions, while those which are reflected 

 from transparent bodies are polarised in one direction only. He ob- 

 served the modifications which parts of organised bodies, whether 

 animal or vegetable, produce on light when they are thin enough to 

 transmit the polarised pencil through them ; and he noticed the 

 coloured and multiplied images which are sometimes seen in Iceland 

 spar. He ascribed these images to the effects of fissures parallel to 

 the longer diagonal of tho crystal rhomboid ; but Sir David Brewster 

 has since ascertained that they arise from veins which act upon the 

 transmitted light at both of their surfaces. 



During the short remainder of his life, Malus continued his scien- 

 tific researches amidst all tbe duties which his post as a member of 

 the Committee of Fortifications required. He was chosen Examiner 

 in Physics and Descriptive Geometry at the Kcole Polytechnique ; 

 and though his health was fast declining, he neglected no occasion of 

 performing tho functions of that office. He was on the point of being 

 made Director of the Studies in that Institution when he was removed 

 by dath from the scene of bis useful labours. 



He died in Fa, February 23rd, 1812, in the thirty-seventh year of 

 bis age; and his wife who, ever since their union, had alleviated his 

 labours by her attentions, and watched him in his last days with 

 affectionate solicitude, survived him but two years. 



Malus enjoyed the esteem of the public for the qualities of his mind, 

 and was beloved by all who knew him for the benevolence of las 

 character. 



(!'J wje de Malta, by Delambre; Biographie Univcrselle.) 



MALVOISINE, WILLIAM DE. [MAWMOISINE.] 



MAMUN, ABUL ABBAS ABDALLAH, the seventh Abbaside 

 caliph, was born at Baghdad in 786. He was entrusted, during the life 

 of his father, the celebrated Harun al liaschid, with the government 

 of Khoraasan ; but on the death of Al Raechid in 808, and the sue- 

 cuion of his brother Amin, Mamun was deprived of this government, 



and commanded to repair to Baghdad. But as such a step would 

 doubtless have been followed by his death, Mamun disobeyed the 

 orders of the caliph, and proclaimed war against him. The contest 

 was carried on till 813, when Baghdad was taken by Thaher and 

 Harthemah, the generals of Mamun, and Amiu put to death. 



The early part of Mamun's reign was greatly disturbed by the pre- 

 tensions of the descendants of Ali, the cousin of Mohammed. [ALL] 

 Mamun, in order to restore peace to his empire, named one of the 

 princes of the house of Ali as his successor, and commanded that the 

 black colour, which distinguished the Abbasides, should be discon- 

 tinued at the court, and replaced by the greeu, which was worn by 

 the descendants of the prophet. This step however occasioned a revo- 

 lution in the government ; the Abbasides rose against their caliph and 

 proclaimed in his stead Ibrahim, the son of Mahadi. After the end 

 of two years, Mamun obtained the caliphate again, and, taught by 

 experience, restored the black colour of the Abbasides, and named 

 his brother as his successor. The partisans of the Alides again 

 rebelled against Mamun, but were unable to obtain any advantages 

 over him. In addition to these wars Mamun was also engaged, during 

 part of his reign, by the revolt of the son of Harthemah in Armenia, 

 and by that of Thaher in Persia. 



In 830 Mamun engaged in a war with Theophilus, the emperor of 

 Constantinople, which is said to have arisen from the refusal of the 

 emperor to allow Leon, a celebrated teacher at Constantinople, to 

 repair to Baghdad, whither he had been invited by the caliph. The 

 war was carried on, principally in Cilicia, during three successive 

 campaigns ; at the close of which Mamun died in the vicinity of 

 Tarsus in 833, and was succeeded by his brother Motasem. 



Although the reign of Mamun was disturbed by so many wars and 

 intestine commotions, yet science and literature were more extensively 

 cultivated than under any preceding caliph. Mamun was a munificent 

 patron of literature ; he founded colleges and libraries in the principal 

 towns of his dominions, and invited to his court not only Greek and 

 Syriac, but also Hindu philosophers and mathematicians. Many of 

 the most celebrated Greek and Hindu works were translated into 

 Arabic by his command ; and among other works written during this 

 time, we may mention an ' Elementary Treatise on Algebra," by 

 Mohammed ben Musa, which was published with a translation by the 

 late Dr. Rosen. [ABBASIDES.] 



MANASSEH, King of Judah, was the .son of Hezekiah, whom ho 

 succeeded in B.C. 696, when only twelve years of age. He abandoned 

 the faith of his father, and became a zealous idolater, setting up an 

 idol in the Temple, and causing his children to pass through fire as a 

 mark of their consecration to Baal. He is said to have practised 

 witchcraft, and gathered wizards around him. I'rophets in vain 

 endeavoured to recall king and people from their vile practices, and 

 " innocent blood filled Jerusalem from one end to the other." After a 

 long continuance in this course, Esar-haddon, the king of Assyria, 

 invaded Judah, captured Jerusalem, and carried Manasseh in chains to 

 Babylon, where he endured a long captivity. In his seclusion he 

 repented of his sins, humbled himself, and prayed to God for deliver- 

 ance. His prayer is said, in 2 Chronicles xxxiii. 19, to be " written among 

 the sayings of the seers;" and a prayer exists, translated from the 

 Greek, which is given at the end of Chronicles, in the edition of the 

 Bible by Christopher Barker in 1589, and is now printed in the 

 Apocrypha. Esar-haddon at length released his captive, and restored 

 him to his kingdom, but rendered him tributary. Manasseh had 

 become wiser from affliction ; as Father Southwell, the Jesuit, has 

 expressed it in his poems 



" King Manasses, unk in depth of in, 

 With plaint! and tears recover'd grace and crown." 



On his return to his kingdom he restored the worship of the true God, 

 repaired the altars, rebuilt the walls of Jerusalem, and garrisoned all 

 his ' fenced cities.' He was unable however to reclaim his people, 

 many of whom had been carried away with himself by Esar-haddon, 

 and their places filled by Assyrians. He died in B.C. 641, and was 

 succeeded by his son Amon. It may be noticed that Manasseh is the 

 only one of the kings of Judah or Israel that bore the name of the 

 founder of a tribe, and none bore that of any of the old patriarchs. 



MANBY, CAPTAIN GEORGE WILLIAM, the author of several 

 inventions applied to the saving of life in shipwreck, was born at 

 Hilgay in Norfolk, on November 28th, 1765, and died at his residence 

 Pedestal House, South town, near Great Yarmouth, on November 18, 

 1854, thus having nearly completed his eighty-ninth year. Ho adopted 

 the military profession, but appears to have retired from any active 

 duty after he had attained the rank of captain in 1803, when however 

 he was appointed barrack-master at Great Yarmouth. Here in 

 February 1807 occurred the loss of the Snipe gun-brig, when he saw 

 sixty-seven persons drowned within a few yards of the beach ; and, 

 in the same gale, so many other disasters occurred that one hun- 

 dred and forty-seven dead bodies were cast upon a line of coast of 

 about thirty miles in extent Such calamities induced him to devise 

 means of assistance by throwing a line over the vessel. This was at 

 first proposed to be done by a balista ; but a successful experiment 

 with a small mortar, when he threw a line over a church led 

 him to prefer the use of gunpowder. Tho groat difficulty to bo 

 overcome was as to the connection of tho shot with the rope. Chains 



