CYCLOID 



CYCLOPS 



689 



were in 1887 authorised by the War OHice to form 

 e\.-le contingents within their ranks, while a 



sjii-ri.-il .-Ncllst ]>s, known an the 20th Middlesex, 



In- Keen railed into existence. These various 

 formations ran hardly In- considered to have as 

 vet won the place they seem destined to occupy, 

 l>ut they have sntli.-ieiitly demonstrated their cap- 

 abilities to cause the highest military authorities 

 to entertain a very hopeful opinion of their value 

 in the near future. 



In America, where cycling is becoming increas- 

 ingly popular, there are a large numltcr of flourish- 

 ing eyolut clubs in the larg^j cities, such as New 

 York', Brooklyn, Philadelphia, Chicago, and Wash- 

 ington; and the cluh-hou.se-, there are more com- 

 plete and better equipped than in Great Britain. 

 One American cyclist is credited with having ridden 

 SIMM) miles in a year, and another 7000 miles. Mr 

 Thomas Stevens, starting from San Francisco on 

 the 22d of April 1884, travelled to Boston, then 

 Clapped to England, again embarked for the Con- 

 tinent, and passed through Germany, Austria- 

 Hungary, the Balkan Peninsula, Asia Minor, Ar- 

 menia, Persia, Afghanistan, India, and China, 

 whence he sailed for his starting-point. This was 

 a ride occupying three years, and involving an 

 enormous amount of endurance, pluck, and energy. 

 Two American students, T. Allen and L. Saditleben, 

 occupied three years in riding round the world, 

 15,044 miles. The popularity of cycling has led to 

 proposals for a tax on cycles ; in France 80,000 

 a year comes from this source. 



Cycling, if rationally pursued, is so exhilarating 

 and health-giving that leading medical men recom- 

 mend its adoption by both sexes in nearly all cases 

 where organic disease is absent. 



See Cyclinrt, by Viscount Bury and G. L. Hillier 

 (Badminton series; new ed. 1895); Spencer's Bicycles 

 and Tricycles, Past and Present (1883), and his 

 Cycle Directory ; Sir B. W. Richardson's Tricycle in 

 Relation to Health and Recreation (1885 ) ; Stables's Health 

 upon Wheels (1885); Pleasures and Adrantaties of Cyclinfl 

 (1887) ; Mecredy and Stoney, Art and Pantimeof Cycling 

 (2d ed. 1893); Stevens, Around the World on a Bicycle 

 (1887); Baudry de Saunier, Histoire Gfnirale de la 

 Velocipede (1891) ; Hillier and Bramson, Amateur Cycling 

 (1893) ; O. Jennings, Cyclinj and Health (new ed. 1893) ; 

 Allen and Sachtleben, Across Asia on a Bicycle (New 

 York, 1894); A. C. Pemberton, The Complete Cyclist 

 (1897); Bicycles and Tricycles, an Elementary Treatise 

 on their Construction, by Archibald Sharp (1897); the 

 C.T.C. Road Books and Inglis's Contour Road Books 

 (1896-97). 



Cy'cloid ( Or. , ' circle-like ' ). If a circle roll along 

 a straight line in its own plane, any point on the 

 circumference describes a curve which is called a 

 cycloid. This is the most interesting of what arc 

 called the transcendental curves, both from its 

 geometrical properties and its numerous applica- 

 tions in mechanics. In dynamics, for example, we 

 find that a heavy particle descends from rest from 

 any point in the arc of an inverted cycloid to the 

 lowest point in the same time exactly, from what- 

 ever point of the curve it starts. This is sometimes 

 expressed by saying that the cycloid is the isochron- 

 ous (Gr., 'equal-time') curve. The Ixxly having 

 reached the lowest point, 

 will, through the im- 

 petus received in the 

 fall, ascend the opposite 

 branch of the curve to 

 a height equal to that 

 from which it fell, and 

 it will employ precisely 

 the same time in ascend- 

 ing as it did in descending. It is clear that if a 

 surface could be procured that would be perfectly 

 smooth and hard, the cycloid would thus present a 



K c 

 The Cycloid. 



solution of the perpetual motion. The line AB, 

 which is called the base of the cycloid, in equal to 

 the circumference of the generating circle ; the 

 length of the curve ADB IB four tune* CD, the 

 diameter ; the evolute of any cycloid is a similar 

 curve of equal length ; and the surface between 

 the curve and its base is three times the area of the 

 circle CD. In any position Kl'l- of the generating 

 circle, AE is equal to the arc EP; PE is the normal 

 at P and = half the radius of curvature ; PF u the 

 tangent to the curve at P. 



Cycloid-scales iish-scales with a round un- 

 tootlied posterior margin and concentric lines par- 

 allel to the latter. See SCALES, FISHES. 



Cyclone ( Or. ky/clos, ' a circle ' ), a circular storm 

 of great force, which, extending over an area of 

 perhaps 500 miles, and revolving round a calm 

 centre, advances at the rate of from 20 to 30 miles 

 an hour. See STORMS. 



Cyclopaedia. See ENCYCLOPEDIA. 



Cyclo'pes ( Or. kuklopes, 'the round-eyed'), in 

 the incoherent traditions of a gradually developing 

 mythology, fall into three groups. ( 1 ) The Homeric 

 Cyclopes, a wild, lawless, and impious race of 

 giants, inhabiting the sea-coasts of Sicily, the most 

 prominent of whom is Polyphemus ( q. v. ). Although 

 Homer does not directly call them one-eyed, yet he 

 expressly terms Polyphemus such, and the later 

 poets attribute his peculiarity to the rest. (2) The 

 three Cyclopes mentioned by Hesiod : Brontes, 

 Steropes, and Arges, each having one eye in the 

 middle of his forehead ; these were sons of Uranus 

 and G;ea, belonged to the race of Titans, and forged 

 thunderbolts for Zeus. Hurled into Tartarus by 

 their father, but delivered by their mother, they 

 helped Kronos to usurp the government of heaven. 

 Kronos, however, in his turn, threw them back to 

 Tartarus, from which they were again released by 

 Zeus, whose servants they now became. Finally, 

 they were slain by Apollo, because they forged the 

 thunderbolt with which Zeus killed yEsculapius. 

 Later tradition placed their workshop in Mount 

 Etna, or in the volcanoes of Lemnos and Lipari, 

 and made them the slaves of Heph.tstus. (3) The 

 Cyclopes mentioned by Strabo as a people who had 

 come from Thrace or Lycia to Argolis, and were 

 distinguished for their skill as builders. 



CYCLOPEAN WALLS is a name given to masonry 

 built of large, irregular stones, closely fitting, but 

 unhewn and uncemented. They were attributed 

 to Strabo's Cyclopes, who were probably mythical, 

 and many of them still exist in Greece (as at 

 Mycenuj and Tiryns), Italy, and elsewhere. More 

 probably the so-called Cyclopean walls were built 

 by some ancient race, perhaps the Pelasgians (q.v.), 

 at a period long anterior to the historical civilisa- 

 tions of Greece and Rome. 



Cyclops* a genus of small fresh-water crus- 

 taceans, type of a family ( Cyclopidje ) in the order 

 Copepoda. They are popularly included under the 

 wide title of ' water-fleas. Various species are com- 

 mon as active swimmers in fresh-water pools or slow- 

 flowing brooks, and a few forms have been recorded 

 from the sea. Like other copepods. cy clops has 

 an elongated body, without a shell, with four 

 forked thoracic feet and a live-jointed alxlomen. 

 The head-region is not distinct from the first ring 

 of the thorax ; there is a pear-shaped segmented 

 body and a long abdomen ; both pairs of antenme 

 are long, and in the male the anterior pair form 

 claspers ; the mandibular and maxillary pains are 

 degenerate ; and a heart is said to ne absent. 

 The average length of the commonest species is 

 from 2 to 3 millimetres ; the males are generally 

 smaller than the females. A very markeu feature, 

 to which the name refers, is the single median eye, 

 usually bright crimson and sparkling like a gem ; 



