636 



HELMINTHOLOGY 



HELPS 



physics. His physiological works are principally 

 connected with the eye, the ear, and the nervous 

 system. Thus, we have his exhaustive treatise on 

 Physiological Optics, his Speculum for the exam- 

 ination of the Retina, his Discourse on Human 

 Vision, and various papers on the means of 

 measuring small periods of time, and their appli- 

 cation to find the rate of propagation of nerve- 

 disturbances. Of a semi-physical nature we have 

 his Analysis of the Spectrum, his explanation of 

 Vowel Sounds (Klangfarbe der Vocalen ; see 

 SOUND), and his papers on the Conservation of 

 Energy with reference to Muscular Action. In 

 physical science he is known by his paper on Con- 

 servation of Energy ( Ueber d. Erhaltung d. Kraft, 

 1847, translated [badly] in Taylor's Scientific 

 Memoirs, new series) ; by a popular lecture on the 

 same subject (1854); by two memoirs in Crelle's 

 Journal, on Vortex-motion in fluids, and on the 

 Vibrations of Air in open pipes, &c., and by 

 several researches into the development of electric 

 current within a galvanic battery. His Populare 

 wissenschaftliche Vortrage appeared in 1865-76 

 (Eng. trans, by Atkinson, with Introduction by 

 Tyndall, 1881 ) ; his great work on Die Lehre der 

 Tonempfindungen (Eng. trans, by Alex. J. Ellis, 

 The Sensations of Tone) in 1862; his Wissenschaft- 

 liche Abhandlungen in 1881-83 ; and his Reden 

 und Vortrage in 1884. He died 8th September 

 1894. 



See Clerk-Maxwell in Nature, vol. xv. ; Riicker in 

 Nature, vol. li. ; and Bezold's German monograph (1895). 



Helminthology, tnat branch of Zoology 

 which treats of worms, especially parasites. 



II H tnoild. a town in the Netherlands, province 

 of North Brabant, lies 23 miles NW. of Venlo by 

 rail. There are manufactures of textiles, machinery, 

 and iron. Pop. (1893) 9328. 



Helmont, JEAN BAPTISTE VAN, Belgian 

 chemist, was born at Brussels in 1577. At Louvain 

 he studied medicine and its cognate sciences, but 

 soon turned aside from them to .throw himself into 

 the movement known as mysticism, to study the 

 works and practise the precepts of Thomas a 

 Kempis and Johann Tauler. Then, falling in 

 with the writings of Paracelsus, he came back 

 to his first love, and began to study chemistry 

 and natural philosophy. After spending several 

 years in France, Switzerland, and England, in 

 1605 he returned to Amsterdam, married Mar- 

 garet van Ranst, a noble lady of Brabant, and 

 in 1609 settled down at his estate near Vilvorde, 

 where he spent the remainder of his life in 

 chemical investigations of various kinds. He 

 died 30th December 1644. In spite of much 

 theosophical mistiness and much alchemical error, 

 Van Helmont is regarded by some historians of 

 chemistry as the greatest chemist who preceded 

 Lavoisier. He was the first to point out the impera- 

 tive necessity for employing the balance in chemis- 

 try, and by its means showed, in many instances, 

 the indestructibility of matter in chemical changes. 

 He paid much attention to the study of gases, and 

 is supposed to have been the first to apply the term 

 gases to elastic aeriform fluids. Of these gases he 

 distinguished several kinds. He was also the first 

 to take the melting-point of ice and the boiling- 

 point of water as standards for the measurement 

 of temperature. It is in his works that the term 

 saturation is first employed, to signify the com- 

 bination of an acid with a base ; and he was one of 

 the earliest investigators of the chemistry of the 

 fluids of the human oody. Along with other phy- 

 siologists of his day, he speculated much on the 

 seat of the soul, which he placed in the stomach. 

 An account of his contributions to the knowledge 

 of chemistry will be found in the Histories of 



Chemistry by Kopp and Hofer. His works, en- 

 titled Ortus Medicince, were published by his son 

 four years after his death, and frequently since 

 then. See Roinmelaere, Etudes sur Van Helmont 

 (Brussels, 1868). 



HellUStedt, a town of Germany, 24 miles by 

 rail ESE. of Brunswick, was formerly famous for 

 its Protestant university, founded by Julius, Duke 

 of Brunswick, in 1574, and suppressed by Jerome 

 Bonaparte in 1809. The university building (the 

 Juleum), which still remains, the 12th-century 

 church of St Stephen, and the Marienberg church 

 are the most noteworthy edifices. Helmstedt grew 

 up originally round the monastery (now in ruins) 

 of St Ludger in the 9th century. Pop, ( 1890) 10,955. 



Helmimd, or HELMAND, a river of Afghani- 

 stan, rises on the south slopes of the Hindu Kush, 

 flows south-west, west, and north-west, and after 

 a course of about 680 miles empties itself into the 

 lake of Hamun or Seistan. See map at AFGHANI- 

 STAN. 



Ilelobia', or MARSH LILIES, form one of the 

 chief groups of Monocotyledons, and comprise the 

 four orders Butomacese, Alismacea?, Juncaginese, 

 and Hydrocharidese. 



Heloderm. See GILA MONSTER. 



II rloisr. See ABELARD. 



Helots were the lowest of the four classes into 

 which the population of ancient Sparta was divided. 

 They are generally supposed to have been the 

 aboriginal population of the country, and to have 

 been reduced to bondage by their Dorian con- 

 querors, their numbers being swelled from time to 

 time by the addition of peoples conquered in war. 

 They belonged to the state, which alone had the 

 power to set them at liberty ; but they toiled for 

 individual proprietors, and were bound to the soil 

 i.e. they could not be sold away from the place of 

 their labour. They were the tillers of the land, for 

 which they paid a rent to their masters ; they 

 served at the public meals, and were occupied on 

 the public works. In war they fought as light 

 troops, each freeborn Spartan (who bore heavy 

 armour) being accompanied to battle by a number 

 of them, sometimes as many as seven. On rare 

 occasions they were equipped as heavy-armed 

 soldiers. It is a matter 01 doubt whether after 

 emancipation they could ever enjoy all the privi- 

 leges of Spartan citizenship. They were treated 

 with much severity by their masters, especially in 

 the later ages of Sparta, and were subjected to 

 degradation and indignities. They were whipped 

 every year, to keep them in mind of their servile 

 state ; they were obliged to wear a distinctive dress 

 ( clothes of sheepskin and a cap of dog's-skin ), and 

 to intoxicate themselves as a warning to the Spar- 

 tan youth ; and when they multiplied to an alarm- 

 ing extent, they were often massacred with the 

 most barbarous cruelty. On one occasion 2000 of 

 them, who had behaved bravely in war, were 

 encouraged to come forward for emancipation, and 

 were then treacherously put to death. The Spar- 

 tans organised, as often as necessity required, secret- 

 service companies (Gr. crypteia) of young men, who 

 went abroad over the country armed with daggers, 

 and both by night and day assassinated the Helots, 

 selecting as their special victims the strongest and 

 most vigorous of the race. 



Helps, SIR ARTHUR, essayist and historian, 

 was born at Streatham, Surrey, 10th July 1813. 

 From Eton he passed to Trinity College, Cam- 

 bridge, where he was thirty-first wrangler in 1835 ; 

 but, what meant more, was admitted a member of 

 the famous Society of the Apostles, among whom 

 were Charles Buller, Maurice, Trench, Monckton 

 Milnes, and Tennyson. On leaving the university lie 



