H E L 



[213 ] 



HEP 



ornamental articles, and is much 

 esteemed. 

 HE'LIX. (e\tg, Gr.) PI. Helices. 



1. The outer bar, or margin, of the 

 external ear. 



2. The snail. A globular or orbi- 

 cular shell ; spire short, convex or 

 conoidal, last whorl ventricose; 

 opening entire, being wider than 

 long ; no operculum. The helix 

 aspera, or common snail, is a well- 

 known illustration. Parkinson ob- 

 serves of the fossil helix, " Shells 

 of this genus are rarely found in a 

 state of petrifaction. The circum- 

 stances of conservation in which 

 they are found are, generally, such 

 as are explicable on the supposition 

 of their having become involved in 

 the gradually accreting tufaceous 

 matter, which is deposited by cer- 

 tain streams and rivers ; or in the 

 stalactitic concretions forming in 

 the cavities of limestone rocks, of 

 comparatively modern formation." 



3. A screw, a spiral. 

 HELMI'NTHOLITE. The name given to 



what have been considered fossil 

 impressions of earth-worms. 



HELMINTHO'IDA. The name given to 

 the second sub-kingdom of the ani- 

 mal kingdom, called also Diplo- 

 neura. This sub-kingdom compre- 

 hends the classes Polygastrica, Eo- 

 tifera, Suctoria, Cirrhopoda, and 

 Annelida. 



HE'LVINE. Tetrahedral garnet. 



HEMI'PTERA. (from ty/ui and wrepov, 

 Gr. So called, because their wing- 

 covers at the base are of a substance 

 resembling horn or leather, and at 

 the tip are membranous.) The 

 eighth order of the class Insecta. 

 These insects have four wings, 

 either stretched straight out, or 

 resting across each other ; the su- 

 perior are coriaceous at their base, 

 with a membranous apex. The 

 mouth of hemipterous insects is 

 adapted for extracting fluids by 

 suction only. 



HEMISPHERE, (hemisphere, Fr. emzs- 



f&ro, It. hemispharium, Lat. rjfua- 

 (fiaipiov, Gr.) The half of a globe 

 when it is supposed to be cut 

 through its centre, in the plane of 

 one of its greatest circles ; one-half 

 of the globe, or sphere, when 

 divided into two by a plane passing 

 through its centre. The equator 

 divides the sphere into two equal 

 parts, called the northern and south- 

 ern hemispheres. The horizon also 

 divides the sphere into two parts, 

 the upper and lower hemispheres. 



HENDE'CAGON. (from evfteica, and ^oWa, 

 Gr.) A figure of eleven faces or 

 angles. 



HEPA'TIC. } (hepaticus, Lat. Jiepati- 



HEPA'TICAL. j que, Fr. epdtico, It.) 

 Belonging to the liver ; pertaining 

 to the liver; resembling liver in 

 form or colour. 



HEPA'TIC CINNABAR. A dark- coloured, 

 steel-grey variety of the mercure 

 sulphure of Haiiy, or cinnabar. 



HEPA'TIC^:. The first order of plants 

 in the class Anogens, comprising 

 the liver- worts. 



HEPA'TIC PYRI'TES. Hepatic sulphuret 

 of iron. A variety of prismatic 

 iron-pyrites, of a yellow colour, 

 which, on exposure to the atmos- 

 phere, acquires a brown tarnish. 

 This embraces those varieties of 

 sulphuret of iron, which are sus- 

 ceptible of a peculiar decomposition, 

 by which the sulphur is more or 

 less disengaged. During this pro- 

 cess the pyrites is converted, wholly 

 or in part, into a compact oxide of 

 iron of a liver- brown colour, from 

 which circumstance it obtains its 

 name. The decomposition begins 

 at the surface, and gradually passes 

 into the centre. 



HE'PATITE. A mineral ; a variety of 

 heavy spar, or sulphate of barytes. 

 This variety is distinguished by 

 its emitting a fetid smell when 

 rubbed, resembling that of sulphu- 

 retted hydrogen, arising from its 

 containing a portion of sulphur. 



HE'PATULE. A name given by Kirwan 



