HARMAN 



3845 



HARMONIC MOTION 



Sir John Harman, 

 English sailor 



After Lely 



Harman, SIB JOHN (d. 1673). 

 English sailor. Of Suffolk birth, he 

 first appears as commanding the 

 Welcome in 

 a battle off 

 Portland in 

 1653. In 1654 

 he sailed to the 

 Mediterranean 

 with Blake, 

 under whom 

 he also fought 

 at Santa Cruz. 

 In 1665 he 

 carried the 

 duke of York's 

 flag in the Royal Charles in the 

 battle of J une 3, when the Dutch 

 were defeated. Knighted for his 

 share in the victory, he was pro- 

 moted rear-admiral and in 1666 

 was severely wounded in the battle 

 off North Foreland. In 1667 he 

 went to the West Indies as com- 

 mander-in-chief and destroyed the 

 French fleet at Martinique. * Carry- 

 ing the campaign ashore, Harman 

 took Cayenne and Surinam. In' 

 1672 he took part in the battle of 

 Sole Bay. Next year he dis- 

 tinguished himself against de Ruy- 

 ter, sitting, owing to illness, in a 

 chair on the deck while directing 

 operations. He died Oct. 11, 1673. 

 Harmattan. Dry, dust-laden 

 wind which blows away from the 

 Sahara between Oct. and March. 

 The harmattan, locally known as 

 the Doctor, brings cool dry weather 

 to the steaming jungles of West 

 Africa, and is health - giving. 

 The quantities of fine dust which it 

 brings are a nuisance. 



Harmer, SIR SIDNEY FBEDKRIC 

 (b. 1862). British scientist. Born at 

 Norwich, March 9, 1862. he 

 educated a t 

 University 

 College, Lon- 

 don, of which 

 he became 

 fellow, and at 

 King's College, 

 C am b ridge, 

 where he was 

 fellow, lecturer 

 and assistant- 

 tutor 1890- 

 1908. He was 



j also superintendent of the univer- 

 sity museum of zoology, Cam- 

 bridge. In 1908 he was appointed 

 director of the natural history 

 departments of the British Museum 

 and keeper of zoology. He was 

 made a F.R.S., and was joint 

 editor of The Cambridge Natural 

 History. He was knighted in 1920. 

 Harmine. Alkaloid which 

 occurs in the seeds of the wild rue 

 (Peganum harmala) The seeds 

 contain about 4 p.c. of alkaloids, 

 one-third of which is harmine, the 

 rest being of harmaline. 



Sir Sidney Harmer. 

 British scientist 



Harmodius and Aristogiton. 



Two devoted Athenian friends. 

 When the sister of Harmodius had 

 been insulted by Hipparchus, 

 brother of the tyrant Hippias, they 

 resolved to murder Hipparchus at 

 the festival of the Panathenaea 

 in 514 B.C. Hipparchus was slain, 

 but Harmodius was killed before 

 Hippias could be reached, and 

 though Aristogiton escaped, he was 

 subsequently taken prisoner. Put 

 to torture, he died without giving 

 any information as to the names of 

 his accomplices. Though the 

 motive of the assassination was to 

 satisfy a private injury, yet the 

 tyranny of Hippias had been so 

 oppressive that Harmodius and 

 Aristogiton were honoured as 

 martyrs by later generations. 



Harxnonds worth. Parish and 

 village of Middlesex, England. It is 

 situated 1 m. S. of the West Dray- 

 ton station of the G.W.R., between 

 Harlington and Colnbrook. Called 

 Hermodesworthe 'in Domesday, 

 the manor once belonged to the 

 Benedictine abbey of Holy Trinity 

 at Rouen, from which it passed to 

 William of Wykeham, who settled 

 it upon Winchester College. The 

 old tithe barn, N.W. of the church, 

 has three floors and an open 

 timber roof. The ancient church of 

 S. Mary the Virgin was restored 

 in 1863-64, when the old brasses 

 were stolen. The manor house 

 was pulled down in 1774 Pron. 

 Harmsworth. 



Harmonia. In Greek legend, 

 daughter of Ares and Aphrodite, 

 and wife of Cadmus. Among her 

 wedding presents were a robe and 

 necklace which brought misfortune 

 on all those who owned them. Ac- 

 cording to one story, they were the 

 gift of Hephaestus, who desired to 

 avenge her mother's unfaithfulness. 

 See Alcmaeon ; Cadmus. 



Harmonica. Musical instru- 

 ment. It consists of glass vessels 

 either selected for their intrinsic 

 notes, or tuned by having water 

 poured into them. Penetrating 

 tones are produced by rubbing the 

 glasses with the moistened finger. 

 The Harmonica, first known in the 

 17th century, was improved by 

 Richard Pockrich, an Irishman, 

 and became a fashionable instru- 

 ment in the middle of the 18th 

 century. It was further developed 

 by Benjamin Franklin, who 

 mounted the glasses on a revolving 

 spindle, their lower edge being made 

 to pass through water. The term also 

 designates a toy having mounted 

 plates of glass, or sometimes metal, 

 struck with a small wooden hammer 



Harmonic Motion. Term 

 which may be used as the general 

 description of the periodic oscilla 

 torv type of motion which is so 



common in nature, and of which the 

 motions of the tides, the vibrations 

 of a violin string, and the beating 

 of a pendulum are familiar ex- 

 amples. The ideally simple type 

 of harmonic motion is known as 

 " simple harmonic motion," and it 

 has been found possible, by the 

 method known as " harmonic 

 analysis," to resolve every har- 

 monic motion into a combination of 

 different simple harmonic motions. 

 Simple harmonic motion is de- 

 fined as follows. If we look at a 

 particle, which is moving uniformly 

 in a circle Q l M Q N, from a point 

 P some distance outside it (see 

 diagram Fig. 1), the particle will 



Fig.l 



appear to be moving backwards 

 and forwards along the dia- 

 meter M O N. While the particle 

 actually moves with uniform speed 

 along the semi-circle N Q 1 M, it will 

 appear to the observer at P to 

 move with increasing speed from 

 N to O, and then with decreasing 

 speed from to M ; its apparent 

 motion is then reversed, and the 

 particle returns to N, again reach- 

 ing its highest apparent velocity 

 when opposite the centre 0. A 

 particle which moves to and fro 

 along a line M O N as the particle 

 considered appears to do, is said to 

 have a simple harmonic motion. 



The bob of a pendulum which is 

 beating small oscillations is an 

 actual example. The maximum 

 distance attained from the centre 

 of the motion is called the ampli- 

 tude, while the time of a complete 

 oscillation backwards and forwards 



Harmonica. A favourite musical 

 instrument of the 18th century 



