ECH 



ECL 



horizon in which the sun is seen to rise 

 at the time of the equinoxes. 



EASTER. This holiday is directed to 

 be celebrated on the first Sunday after 

 the full moon which happens next after 

 the 21st of March ; this, being the four- 

 teenth day of the first Jewish month, 

 corresponds with the first day of the week 

 after the Passover, the anniversary of 

 the Resurrection of Christ. The time at 

 which this day must happen varies with 

 the year ; but the limits within which it 

 must fall are the 22nd of March and the 

 25th of April, inclusive, making a period 

 of thirty-five days. 



EBULLITION (ebullitio, a bubbling 

 up). The boiling or bubbling of liquids ; 

 the production of vapour at the boiling 

 point. 



EBURNI'NiE. A subfamily of the 

 Turbinellidce, or Turnip-shells, named 

 from the typical genus eburna, and hav- 

 ing the base of the shell truncate and 

 notched, the pillar smooth, and the inner 

 lip considerably thickened and spreading. 



ECCE'NTRIC (eK, out, Kevrpov, the 

 centre). A term applied to circles and 

 spheres which have not the same centre, 

 and consequently are not parallel; in 

 opposition to concentric, which denotes a 

 common centre, and therefore paral- 

 lelism. 



Eccentricity. The distance of the 

 centre of the orbit of a planet from th« 

 centre of the sun ; that is, the distance 

 between the centre of the ellipsis and the 

 focus. 



E'CDYSIS (eKivtrii, the act of strip- 

 ping). Moulting of the skin. 



ECHTNATE (ex^vof, the sea-hedge- 

 hog). Bristly ; covered with stiff hairs 

 or prickles, like an echinus ; a term ap- 

 plied to bristly fruits, as that of the sweet 

 chestnut, &c. 



ECHI'NID^ {ex^voi, the sea-liedge- 

 hog). A family of radiated animais. 

 comprehending those marine animals 

 commonly known by the name of sea- 

 eggs or sea-urchins, and constituting, 

 according to De Blainville, the second 

 order of the class Echinodermata. By 

 the term echini, geologists denote the 

 calcareous petrifactions of the echinus, 

 which occur through all the formations, 

 from the epoch of the transition series to 

 the present time. 



ECHI'NODE'RMATA (exli/oc, the sea- 

 hedgehog, hepixa, skin). A class of the 

 Radiata, comprising aquatic invertebrate 

 animals, which have the surface of their 

 skin generally covered with calcareous 

 115 



spines, as the common sea-urchin and 

 the star-fish. The following orders have 

 been founded on differences of their 

 general form : — 



1. Crino'ida, or those species, chiefly 

 fossil, which are fixed by a jointed pe- 

 duncle, and have long ramified articu- 

 lated tentacula extending from around 

 the abdominal cavity, as in encrinus and 

 pentacrinus. 



2. Aster ida or Stellerida, comprising 

 the articulated, free, flexible, stellated 

 species, which are destitute of peduncle, 

 and with a short axis, as in asteria. 



3. Echinida, in which the body is in- 

 flexible and covered with a solid articu- 

 lated shell, the exterior surface being 

 covered with moveable calcareous spines, 

 as in echinus. 



4. Holothurida, in which the axis of 

 the body is placed horizontally, and there 

 is a soft, coriaceous skin, seldom pro- 

 tected with spines, as in holothuria. — 

 Grant. 



E'CHO (r;xw, a sound ; especially, a 

 returned sound). A wave of sound, 

 which, falling perpendicularly on a re- 

 flecting surface, returns in the same 

 direction, and arrives at the spot from 

 which it originated. 



ECLIPSE (eK\ci>^<9, a defect). A 

 lunar eclipse is caused by the projection 

 of a shadow upon the (full) moon, in 

 consequence of the interception of the 

 sun's rays by the earth. A solar eclipse 

 is occasioned by the interception of a 

 part or of the whole of the sun's rays, by 

 the (new) moon. The eclipse is partial, 

 when the moon hides only a part of the 

 sun's disk ; total, when she covers the 

 whole of it; annular, when the sun, 

 masked by the moon, projects all round 

 in the form of a luminous ring ; central, 

 when the spectator's place is in the pro- 

 longation of the line joining the centres 

 of the sun and the moon. 



ECLI'PTIC (€K\ei4fis, an eclipse). The 

 orbit described apparently by the sun 

 round the earth, and in reality by the 

 earth round the sun. It is named from 

 the circumstance that all eclipses can 

 happen only when the moon is in the 

 same plane, or very near it. The lowest 

 and highest points of the ecliptic are the 

 winter and summer solstices respectively. 

 See Solstice. 



I. Ecliptic, Obliquity of. The inclina- 

 tion of the ecliptic to the equator of the 

 earth, amounting to an angle of 23° 28'. 

 This inclination gives rise to the pheno- 

 mena of the seasons. 



