HER 



HET 



plants. Cellular, flowerless plants, con- 

 sisting of an axis or stem, either leafy or 

 bordered : reproductive organs are valved 

 thecce of different kinds. 



HE'PATITE (iiTrap, liver). A variety 

 of heavy spar, or sulphate of barytes, 

 containing a minute portion of sulphur, 

 and emitting, when heated or rubbed, a 

 fetid sulphurous odour. 



HE'PATULE {nnap, liver). The name 

 given by Kirwan to the hydrosulphuret of 

 other writers. 



HE'PTAGON (^TTTci, seven, ywv/a, 

 angle). In Geometry, a plane figure of 

 seven sides. The area of a regular hep- 

 tagon is equal to the square of one of its 

 sides multiplied into the constant num- 

 ber 3.6339124, or seven-fourths of the 

 tangent of the angle at the base to ra 

 dius 1. 



Heptagonal Numbers. A kind of po- 

 lygonal numbers in which the difference 

 of the terms of the corresponding arith- 

 metical progression is 5, thus, — 



Arithmeticals—l, 6, 11, 16, 21, 26, &c. 



Heptagonals— 1, 7, 18, 34, 55, 81, &c., 

 where the heptagonals are formed by 

 adding continually the terms of the arith- 

 meticals, above them, whose common 

 difference is 5. 



HEPTAGY'NIA (eTrra, seven, fvvt), a 

 woman). The name of those orders of 

 plants in the system of Linnaeus, which 

 are characterized by the presence of seven 

 pistils. 



HEPTA'NDRIA (kirra, seven, uv'rjp, a 

 man). The seventh class of the Linnaean 

 system of plants, characterized by the 

 presence of seven stamens. 



HERBA'RIUM (herba, a herb). A 

 collection of dried specimens of plants, 

 formerly known by the expressive term 

 hortus siccus, or dried garden. 



HER'CULES. Eugonasia. A northern 

 constellation, consisting of 113 stars. 

 This constellation has also been named 

 Hercules cum Ramo et Cerbero. Its prin- 

 cipal star is called Ras Algratha. 



HE'RDERITE. The prismatic fluor- 

 haloid of Mohs ; a mineral found in 

 crystals imbedded in fluor, in Saxony, 

 and named from Herder, its discoverer. 



HERMA'PHRODITE ('Ep^rif, Mer- 

 cury, 'A0po5/Tfj, Venus). A term ap- 

 plied, iu' Botany, to plants in which the 

 stamen and the pistil are contained in 

 the same flower; all other flowering 

 plants being termed unisexual, as monoe- 

 cious and dioecious plants. 



HERME'TIC SEAL. The closure of 

 the end of a glass vessel when heated to 

 163 



the melting point. The name is derived 

 from the Egyptian Hermes, supposed to 

 have been the father of chemistry, which 

 has hence been called the Plermetic 

 art. 



HERO'S FOUNTAIN. An apparatus 

 in which the compression of air is em- 

 ployed to produce a jet of water. Hero's 

 Ball is a similar contrivance for the same 

 purpose. Hero's steam-engine is a con- 

 trivance for producing a rotatory motion 

 by means of steam, and was invented 

 120 years before the present era. 



HERPETO'LOGY {^pnerop, a reptile, 

 Xo-yop, a description). That branch of 

 Zoology which treats of the structure, 

 history, and classification of Reptiles. 



HER'SCHELorU'RANUS. The most 

 remote, but one, of the planets, accom- 

 plishing its revolution round the sun in 

 eighty-four years. Its time of diurnal 

 rotation is not determined. 



HE'RSCHELITE. A mineral found 

 in olivine, brought by Mr. Herschel from 

 Sicily. 



HESPE'RIDIN. A crystalline sub- 

 stance, obtained from the skin of the 

 unripe orange or lemon. 



HESPERI'DIUM. A many-celled, 

 superior, in dehiscent fruit, covered by a 

 spongy separable rind, as the orange. 



HE'TEPOSITE. A phosphate of iron 

 and manganese, found at Haute Vienne. 



HE'TERO- CeTepoi, the other, one of 

 two). A Greek term, in composition 

 generally denoting difference, and thus 

 distinguished from the term homo-, which 

 indicates resemblance : — 



1. Hetero-branchiata {jipa-fx^a, gills). 

 The name given by Blainville to the 

 fourth order of his Acephalophora. 



2. Hetero-carpien (fcapTroc, fruit). A 

 term applied by Desvaux to that kind of 

 fruit which is more commonly called 

 inferior, from its contracting adhesions 

 with other organs. On the same prin- 

 ciple, he designated superior fruits as 

 auto-carpien, owing to their freedom 

 from such adhesions. 



3. Hetero-cephalous {Ke<pa\ti, the head). 

 A term applied by De Candolle to those 

 plants in which some of the capitula are 

 composed entirely of male flowers, and 

 others entirely of female flowers. 



4. Hetero-cercal{KepKos, a tail of a beast). 

 A term applied to the tail of all the palae- 

 ozoic fishes : their back-bone runs to a 

 point above the tail, which is placed be- 

 below, like a triangular rudder. This 

 structure is still seen in our sharks, 

 sturgeons, and in the sauroids of the 



