H E L 



H E T 



ter, which is deposited by certain streams 

 and rivers ; or in the stalactitic concre- 

 tions forming in the cavities of limestone 

 rocks, of comparatively modern forma- 

 tion." It is observed that the terrestrial 

 univalves are never armed with spines, 

 tubercles, or other elevations, but exhibit 

 generally a levigated shell. 



HE'LVINE. Tetrahedral garnet. 



HE'MATITE. (a</tan'r?;> Gr.) Iron ore. 

 There are two kinds of hematite, the red 

 hematite, or rhombohedral iron-ore, and 

 the brown hematite, or prismatic iron-ore. 

 Also written Haematite. 



HEMATI'TIC. Composed of hematite; con- 

 taining hematite ; resembling hematite. 



HEMI'PTERA. (from ijfj.i<rv and Trrtpov, 

 Gr. So called, because their wing-covers 

 at the base are of a substance resembling 

 horn or leather, and at the tip are mem- 

 branous.) An order of insects, compris- 

 ing two families, Geocorisse and Hydro- 

 corisse. TheSe insects have four wings, 

 either stretched straight out, or resting 

 across each other; the superior are co- 

 riaceous at their base, with a membranous 

 apex. The mouth of hemipterous insects 

 is adapted for extracting fluids by suction 

 only. They are carnivorous, or, more 

 properly, animal- suckers. The cockroach, 

 locust, grasshopper, bug, lantern-fly, &c., 

 belong to this order. 



HEMI'PTERAL. ) Belonging to the order 



HEMI'PTEROUS. $ Hemiptera ; insects 

 which have one-half of their wings coria- 

 ceous, and the other half membranous. 



HE'MISPHERE. (hemisphere, Fr. emisfero, 

 It. hemispheerium, Lat. jjfiiatyaipiov, 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 

 southern hemispheres. The horizon also 

 divides the sphere into two parts, the 

 upper and the lower hemispheres. 



.-** 



HEMISPHERIC*. half a globe. 



HENDE'CAGON. (from IVOCME and ywj/t'a, 

 Gr.) A figure of eleven faces or angles. 



HEPA'TIC. ) (hepaticus, Lat. hepatigue, 



HEPA'TICAL. $ Fr. epatico, It.) Belong- 

 ing to the liver ; pertaining to the liver. 



HEPA'TIC CINNABAR. A dark-coloured, 

 steel-grey variety of the mercure sulphure 

 of Haiiy, or cinnabar. 



HEPA'TIC PYRI'TES. Hepatic sulphuret of 

 iron. A variety of prismatic iron-pyrites, 

 of a yellow colour, which, on exposure to 

 the atmosphere, acquires a brown tarnish. 

 This embraces those varieties of sulphuret 

 of iron, which are susceptible of a pecu- 



liar decomposition, by which the sulphur 

 is more or less disengaged. During this 

 process the pyrites is converted, wholly or 

 in part, into a compact oxide of iron of a 

 liver-brown colour, from which circum- 

 stance it obtains its name. In conse- 

 quence of this decomposition, the mass 

 does not lose its original form, but its 

 hardness and specific gravity are somewhat 

 diminished, and its lustre disappears. 

 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 

 sulphuretted hydrogen, arising from its 

 containing a portion of sulphur. 



HE'PATULE. A name given by Kirwan to 

 certain combinations called by others hy- 

 drosulphurets. 



HEPTACA'PSULAR. (from sVrd, Gr. and 

 capsula, Lat.) Having seven cells. 



HE'PTAGON. (heptagone et eptagone, Fr. 

 ettagono, It. STTTU and ywria, Gr.) A 

 figure having seven sides and as many 

 angles. 



HEPTA'GONAL. Having seven sides and as 

 many angles. 



HERBA'CEOUS. (herbaceus, Lat.) Plants 

 that perish annually down to the roots, 

 having succulent stems, or stalks. Of 

 herbaceous plants, some are annual, these 

 perish, stem and root, every year ; some 

 are biennial, the roots subsisting two 

 years ; others are perennial, being perpe- 

 tuated for many years by their roots, a 

 new stem springing up every year. 



HERBA'RIUM. (herbarius, Lat.) A col- 

 lection of dried plants ; a place set apart 

 for growing herbs in. 



HERBI'VOROUS. (from herba and voro, 

 Lat. to devour.) Subsisting on vegeta- 

 bles. 



HERMA'PHRODITE. (from 'Epfjirjz, Mer- 

 cury, and 'AtypodiTT), Venus, htrmapho- 

 dite, Fr. ermaphrodito, It. A fabulous 

 name, compounded of those of Mercury 

 and Venus, Hermes and Aphrodite.) 



1. Having both the male and female parts 

 of generation. 



2. In botany, plants are so called which 

 contain both stamens and ovarium, in 

 distinction to monoecious and dioecious 

 plants. 



HERPETO'LOGIST. One skilled in the na- 

 tural history of insects. 



HERPETO'LOGY. (tpirfTog and \6yo, Gr. ) 

 That branch of natural history which 

 treats of reptiles, their habits, &c. 



HERSCHELI'TE. A mineral of a white co- 

 lour, found by Herschel in olivine, and 

 named after its discoverer. 



HETEROCLI'TICAL. In conchology, revers- 

 ed ; a term applied to shells whose spires 



