Scott, with whom she and her boys afterwards stayed some time at
Abbotsford. "There are some whom we meet, and should like ever after to
claim as kith and kin; and you are one of those," was Scott's compliment
to her at parting. One of the results of her Edinburgh visit was an
article, full of praise, judiciously tempered with criticism, by Jeffrey
himself for the _Edinburgh Review_. Mrs Hemans returned to Wavertree to
write her _Songs of the Affections_, which were published early in 1830.
In the following June, however, she again left home, this time to visit
Wordsworth and the Lake country; and in August she paid a second visit
to Scotland. In 1831 she removed to Dublin. Her poetry of this date is
chiefly religious. Early in 1834 her _Hymns for Childhood_, which had
appeared some years before in America, were published in Dublin. At the
same time appeared her collection of _National Lyrics_, and shortly
afterwards _Scenes and Hymns of Life_. She was planning also a series of
German studies, one of which, on Goethe's _Tasso_, was completed and
published in the _New Monthly Magazine_ for January 1834. In intervals
of acute suffering she wrote the lyric _Despondency and Aspiration_, and
dictated a series of sonnets called _Thoughts during Sickness_, the last
of which, "Recovery," was written when she fancied she was getting well.
After three months spent at Redesdale, Archbishop Whately's country
seat, she was again brought into Dublin, where she lingered till spring.
Her last poem, the _Sabbath Sonnet_, was dedicated to her brother on
Sunday April 26th, and she died in Dublin on the 16th of May 1835 at the
age of forty-one.
Mrs Hemans's poetry is the production of a fine imaginative and
enthusiastic temperament, but not of a commanding intellect or very
complex or subtle nature. It is the outcome of a beautiful but
singularly circumscribed life, a life spent in romantic seclusion,
without much worldly experience, and warped and saddened by domestic
unhappiness and physical suffering. An undue preponderance of the
emotional is its prevailing characteristic. Scott complained that it was
"too poetical," that it contained "too many flowers" and "too little
fruit." Many of her short poems, such as "The Treasures of the Deep,"
"The Better Land," "The Homes of England," "Casabianca," "The Palm
Tree," "The Graves of a Household," "The Wreck," "The Dying
Improvisatore," and "The Lost Pleiad," have become standard English
lyrics. It is on the strength of these that her reputation must rest.
Mrs Hemans's _Poetical Works_ were collected in 1832; her _Memorials_
&c., by H. F. Chorley (1836).
HEMEL HEMPSTEAD, a market-town and municipal borough in the Watford
parliamentary division of Hertfordshire, England, 25 m. N.W. from
London, with a station on a branch of the Midland railway from
Harpenden, and near Boxmoor station on the London and North Western main
line. Pop. (1891) 9678; (1901) 11,264. It is pleasantly situated in the
steep-sided valley of the river Gade, immediately above its junction
with the Bulbourne, near the Grand Junction canal. The church of St Mary
is a very fine Norman building with Decorated additions. Industries
include the manufacture of paper, iron founding, brewing and tanning.
Boxmoor, within the parish, is a considerable township of modern growth.
Hemel Hempstead is governed by a mayor, 6 aldermen and 18 councillors.
Area, 7184 acres.
Settlements in the neighbourhood of Hemel Hempstead (_Hamalamstede_,
_Hemel Hampsted_) date from pre-Roman times, and a Roman villa has been
discovered at Boxmoor. The manor, royal demesne in 1086, was granted by
Edmund Plantagenet in 1285 to the house of Ashridge, and the town
developed under monastic protection. In 1539 a charter incorporated the
bailiff and inhabitants. A mayor, aldermen and councillors received
governing power by a charter of 1898. The town has never had
parliamentary representation. A market on Thursday and a fair on the
feast of Corpus Christi were conferred in 1539. A statute fair, for long
a hiring fair, originated in 1803.
HEMEROBAPTISTS, an ancient Jewish sect, so named from their observing a
practice of daily ablution as an essential part of religion. Epiphanius
(_Panarion_, i. 17), who mentions their doctrine as the fourth heresy
among the Jews, classes the Hemerobaptists doctrinally with the
Pharisees (q.v.) from whom they differed only in, like the Sadducees,
denying the resurrection of the dead. The name has been sometimes given
to the Mandaeans on account of their frequent ablutions; and in the
_Clementine Homilies_ (ii. 23) St John the Baptist is spoken of as a
Hemerobaptist. Mention of the sect is made by Hegesippus (see Euseb.
_Hist. Eccl._ iv. 22) and by Justin Martyr in the _Dialogue with
Trypho_, S 80. They were probably a division of the Essenes.
HEMICHORDA, or HEMICHORDATA, a zoological term introduced by W. Bateson
in 1884, without special definition, as equivalent to Enteropneusta,
which then included the single genus _Balanoglossus_, and now generally
employed to cover a group of marine worm-like animals believed by many
zoologists to be related to the lower vertebrates and so to represent
the invertebrate stock from which Vertebrates have been derived.
Vertebrates, or as they are sometimes termed Chordates, are
distinguished from other animals by several important features. The
chief of these is the presence of an elastic rod, the notochord, which
forms the longitudinal axis of the body, and which persists throughout
life in some of the lowest forms, but which appears only in the embryo
of the higher forms, being replaced by the jointed backbone or vertebral
column. A second feature is the development of outgrowths of the pharynx
which unite with the skin of the neck and form a series of perforations
leading to the exterior. These structures are the gill-slits, which in
fishes are lined with vascular tufts, but which in terrestrial breathing
animals appear only in the embryo. The third feature of importance is
the position of structure of the central nervous system, which in all
the Chordates lies dorsally to the alimentary canal and is formed by the
sinking in of a longitudinal media dorsal groove. Of these structures
the Vertebrata or Craniata possess all three in a typical form; the
Cephalochordata (see Amphioxus) also possess them, but the notochord
extends throughout the whole length of the body to the extreme tip of
the snout; the Urochordata (see TUNICATA) possess them in a larval
condition, but the notochord is present only in the tail, whilst in the
adult the notochord disappears and the nervous system becomes profoundly
modified; in the Hemichorda, the respiratory organs very closely
resemble gill-slits, and structures comparable with the notochord and
the tubular dorsal nervous system are present.
The Hemichorda include three orders, the Phoronidea (q.v.), the
Pterobranchia (q.v.) and the Enteropneusta (see BALANOGLOSSUS), but the
relationship to the Chordata expressed in the designation Hemichordata
cannot be regarded as more than an attractive theory with certain
arguments in its favour. (P. C. M.)
HEMICYCLE (Gr. [Greek: hemi-], half, and [Greek: kyklos], circle), a
semicircular recess of considerable size which formed one of the most
conspicuous features in the Roman Thermae, where it was always covered
with a hemispherical vault. A small example exists in Pompeii, in the
street of tombs, with a seat round inside, where those who came to pay
their respects to the departed could rest. An immense hemicycle was
designed by Bramante for the Vatican, where it constitutes a fine
architectural effect at the end of the great court.
HEMIMERUS, an Orthopterous or Dermapterous insect, the sole
representative of the family _Hemimeridae_, which has affinities with
both the _Forficulidae_ (earwigs) and the _Blattidae_ (cockroaches).
Only two species have been discovered, both from West Africa. The better
known of these (_H. hanseni_) lives upon a large rat-like rodent
(_Cricetomys gambianus_) feeding perhaps upon its external parasites,
perhaps upon scurf and other dermal products. Like many epizoic or
parasitic insects, _Hemimerus_ is wingless, eyeless and has relatively
short and strong legs. Correlated also with its mode of life is the
curious fact that it is viviparous, the young being born in an advanced
stage of growth.
HEMIMORPHITE, a mineral consisting of hydrous zinc silicate, H2Zn2SiO5,
of importance as an ore of the metal, of which it contains 54.4%. It is
interesting crystallographically by reason of the hemimorphic
development of its orthorhombic crystals; these are prismatic in habit
and are differently terminated at the two ends. In the figure, the faces
at the upper end of the crystal are the basal plane k and the domes o,
p, l, m, whilst at the lower end there are only the four faces of the
pyramid P. Connected with this polarity of the crystals is their
pyroelectric character--when a crystal is subjected to changes of
temperature it becomes positively electrified at one end and negatively
at the opposite end. There are perfect cleavages parallel to the prism
faces (d in the figure). Crystals are usually colourless, sometimes
yellowish or greenish, and transparent; they have vitreous lustre. The
hardness is 5, and the specific gravity 3.45. The mineral also occurs as
stalactitic or botryoidal masses with a fibrous structure, or in a
massive, cellular or granular condition intermixed with calamine and
clay. It is decomposed by hydrochloric acid with gelatinization; this
property affords a ready means of distinguishing hemimorphite from
calamine (zinc carbonate), these two minerals being, when not
crystallized, very like each other in appearance. The water contained in
hemimorphite is expelled only at a red heat, and the mineral must
therefore be considered as a basic metasilicate, (ZnOH)2SiO3.
[Illustration]
The name hemimorphite was given by G. A. Kenngott in 1853 because of the
typical hemimorphic development of the crystals. The mineral had long
been confused with _calamine_ (q.v.) and even now this name is often
applied to it. On account of its pyroelectric properties, it was called
_electric calamine_ by J. Smithson in 1803.
Hemimorphite occurs with other ores of zinc (calamine and blende),
forming veins and beds in sedimentary limestones. British localities are
Matlock, Alston, Mendip Hills and Leadhills; at Roughten Gill, Caldbeck
Fells, Cumberland, it occurs as mammillated incrustations of a sky-blue
colour. Well-crystallized specimens have been found in the zinc mines at
Altenberg near Aachen in Rhenish Prussia, Nerchinsk mining district in
Siberia, and Elkhorn in Montana. (L. J. S.)
HEMINGBURGH, WALTER OF, also commonly, but erroneously, called WALTER
HEMINGFORD, a Latin chronicler of the 14th century, was a canon regular
of the Austin priory of Gisburn in Yorkshire. Hence he is sometimes
known as Walter of Gisburn (Walterus Gisburnensis). Bale seems to have
been the first to give him the name by which he became more commonly
known. His chronicle embraces the period of English history from the
Conquest (1066) to the nineteenth year of Edward III., with the
exception of the years 1316-1326. It ends with the title of a chapter in
which it was proposed to describe the battle of Crecy (1346); but the
chronicler seems to have died before the required information reached
him. There is, however, some controversy as to whether the later
portions which are lacking in some of the MSS. are by him. In compiling
the first part, Hemingburgh apparently used the histories of Eadmer,
Hoveden, Henry of Huntingdon, and William of Newburgh; but the reigns of
the three Edwards are original, composed from personal observation and
information. There are several manuscripts of the history extant--the
best perhaps being that presented to the College of Arms by the earl of
Arundel. The work is correct and judicious, and written in a pleasing
style. One of its special features is the preservation in its pages of
copies of the great charters, and Hemingburgh's versions have more than
once supplied deficiencies and cleared up obscurities in copies from
other sources.
The first three books were published by Thomas Gale in 1687, in his
_Historiae Anglicanae scriptores quinque_, and the remainder by Thomas
Hearne in 1731. The first portion was again published in 1848 by the
English Historical Society, under the title _Chronicon Walteri de
Hemingburgh, vulgo Hemingford nuncupati, de gestis regum Angliae_,
edited by H. C. Hamilton.
HEMIPTERA (Gr. [Greek: hemi-], half and [Greek: pteron], a wing), the
name applied in zoological classification to that order of the class
Hexapoda (q.v.) which includes bugs, cicads, aphids and scale-insects.
The name was first used by Linnaeus (1735), who derived it from the
half-coriaceous and half-membranous condition of the forewing in many
members of the order. But the wings vary considerably in different
families, and the most distinctive feature is the structure of the jaws,
which form a beak-like organ with stylets adapted for piercing and
sucking. Hence the name _Rhyngota_ (or _Rhynchota_), proposed by J. C.
Fabricius (1775), is used by many writers in preference to Hemiptera.
[Illustration: After Marlatt, _Bull._ 14 (N.S.) _Div. Ent. U.S. Dept.
Agr._
FIG. 1.--Head and Prothorax of Cicad from side.
I., Frons.
II., Base of mandible.
III., Base of first maxillae.
IV., Second maxillae forming rostrum.
V., Pronotum.]
_Structure._--The head varies greatly in shape, and the feelers have
usually but few segments--often only four or five. The arrangement of
the jaws is remarkably constant throughout the order, if we exclude from
it the lice (_Anoplura_). Taking as our type the head of a cicad, we
find a jointed rostrum or beak (figs. 1 and 2, IV. b, c) with a deep
groove on its anterior face; this organ is formed by the second pair of
maxillae and corresponds therefore to the labium or "lower lip" of
biting insects. Within the groove of the rostrum two pairs of slender
piercers--often barbed at the tip--work to and fro. One of these pairs
(fig. 2, II. a, b, c) represents the mandibles, the other (fig. 2, III.
a, b, c) the first maxillae. The piercing portions of the
latter--representing their inner lobes or laciniae--lie median to the
mandibular piercers in the natural position of the organs. These
homologies of the hemipterous jaws were determined by J. C. Savigny in
1816, and though disputed by various subsequent writers, they have been
lately confirmed by the embryological researches of R. Heymons (1899).
Vestigial palps have been described in various species of Hemiptera, but
the true nature of these structures is doubtful. In front of the rostrum
and the piercers lies the pointed flexible labrum and within its base a
small hypopharynx (fig. 2, IV. d) consisting of paired conical
processes which lie dorsal to the "syringe" of the salivary glands. This
latter organ injects a secretion into the plant or animal tissue from
which the insect is sucking. The point of the rostrum is pressed against
the surface to be pierced; then the stylets come into play and the fluid
food is believed to pass into the mouth by capillary attraction.
[Illustration: After Marlatt, _Bull. 14_ (N.S.) _Div. Ent. U.S. Dept.
Agr._
FIG. 2.--Head and Prothorax of Cicad, parts separated.
I., a, frons; b, clypeus; c, labrum; d, epipharynx.
I'., Same from behind.
II., Mandible.
III., 1st maxillae, a, base; b, sheath; c, stylet; c', muscle.
IV., 2nd maxillae, a, sub-mentum; b, mentum; c, ligula, forming beak;
d, hypopharynx (shown also from front d', and behind d").
V., Prothorax, b, haunch; a, trochanter.]
The prothorax (figs. 1 and 2, V.) in Hemiptera is large and free, and
the mesothoracic scutellum is usually extensive. The number of tarsal
segments is reduced; often three, two or only one may be present instead
of the typical insectan number five. The wings will be described in
connexion with the various sub-orders, but an interesting peculiarity of
the Hemiptera is the occasional presence of winged and wingless races of
the same species. Eleven abdominal segments can be recognized, at least
in the early stages; as the adult condition is reached, the hinder
segments become reduced or modified in connexion with the external
reproductive organs, and show, in some male Hemiptera, a marked
asymmetry. The typical insectan ovipositor with its three pairs of
processes, one pair belonging to the eighth and two pairs to the ninth
abdominal segment, can be distinguished in the female.
[Illustration: After Marlatt, _Bull. 4_ (N.S.) _Div. Ent. U.S. Dept.
Agr._
FIG. 3.--a, Cast-off nymphal skin of Bed-bug (_Cimex lectularius_); b,
Second instar after emergence from a; c, The same after a meal.]
In the nervous system the concentration of the trunk ganglia into a
single nerve-centre situated in the thorax is remarkable. The digestive
system has a slender gullet, a large crop and no gizzard; in some
Hemiptera the hinder region of the mid-gut forms a twisted loop with the
gullet. Usually there are four excretory (Malpighian) tubes; but there
are only two in the _Coccidae_ and none in the _Aphidae_. "Stink
glands," which secrete a nauseous fluid with a defensive function, are
present in many Hemiptera. In the adult there is a pair of such glands
opening ventrally on the hindmost thoracic segment, or at the base of
the abdomen; but in the young insect the glands are situated dorsally
and open to the exterior on a variable number of the abdominal terga.
_Development._--In most Hemiptera the young insect (fig. 3) resembles
its parents except for the absence of wings, and is active through all
stages of its growth. In all Hemiptera the wing-rudiments develop
externally on the nymphal cuticle, but in some families--the cicads for
example--the young insect (fig. 10) is a larva differing markedly in
form from its parent, and adapted for a different mode of life, while
the nymph before the final moult is sluggish and inactive. In the male
_Coccidae_ (Scale-insects) the nymph (fig. 4) remains passive and takes
no food. The order of the Hemiptera affords, therefore, some interesting
transition stages towards the complete metamorphosis of the higher
insects.
[Illustration: After Riley and Howard, _Insect Life_, vol. i. (U.S.
Dept. Agr.).
FIG. 4.--Passive Nymph or "Pupa" of male scale-insect (_Icerya_).]
_Distribution and Habits._--Hemiptera are widely distributed, and are
plentiful in most quarters of the globe, though they probably have not
penetrated as far into remote and inhospitable regions as have the
Coleoptera, Diptera and Aptera. They feed entirely by suction, and the
majority of the species pierce plant tissues and suck sap. The leaves of
plants are for the most part the objects of attack, but many aphids and
scale-insects pierce stems, and some go underground and feed on roots.
The enormous rate at which aphids multiply under favourable conditions
makes them of the greatest economic importance, since the growth of
immense numbers of the same kind of plant in close proximity--as in
ordinary farm-crops--is especially advantageous to the insects that feed
on them. Several families of bugs are predaceous in habit, attacking
other insects--often members of their own order--and sucking their
juices. Others are scavengers feeding on decaying organic matter; the
pond skaters, for example, live mostly on the juices of dead floating
insects. And some, like the bed-bugs, are parasites of vertebrate
animals, on whose bodies they live temporarily or permanently, and whose
blood they suck.
The Hemiptera are especially interesting as an order from the variety of
aquatic insects included therein. Some of these--the _Hydrometridae_ or
pond-skaters, for example--move over the surface-film, on which they are
supported by their elongated, slender legs, the body of the insect being
raised clear of the water. They are covered with short hairs which form
a velvet-like pile, so dense that water cannot penetrate. Consequently
when the insect dives, an air-bubble forms around it, a supply of oxygen
is thus secured for breathing and the water is kept away from the
spiracles. In many of these insects, while most individuals of the
species are wingless, winged specimens are now and then met with. The
occasional development of wings is probably of service to the species in
enabling the insects to reach new fresh-water breeding-grounds. This
family of Hemiptera (the _Hydrometridae_) and the _Saldidae_ contain
several insects that are marine, haunting the tidal margin. One genus of
_Hydrometridae_ (_Halobates_) is even oceanic in its habit, the species
being met with skimming over the surface of the sea hundreds of miles
from land. Probably they dive when the surface becomes ruffled. In these
marine genera the abdomen often undergoes excessive reduction (fig. 5).
Other families of Hemiptera--such as the "Boatmen" (_Notonectidae_) and
the "Water-scorpions" (fig. 6) and their allies (_Nepidae_) dive and
swim through the water. They obtain their supply of air from the
surface. The _Nepidae_ breathe by means of a pair of long, grooved tail
processes (really outgrowths of the abdominal pleura) which when
pressed together form a tube whose point can pierce the surface film and
convey air to the hindmost spiracles which are alone functional in the
adult. The _Notonectidae_ breathe mostly through the thoracic spiracles;
the air is conveyed to these from the tail-end, which is brought to the
surface, along a kind of tunnel formed by overlapping hairs.
[Illustration: After Carpenter, _Proc. R. Dublin Soc._, vol. viii.
FIG. 5.--A reef-haunting hemipteron (_Hermatobates haddonii_) with
excessively reduced abdomen. Magnified.]
[Illustration: FIG. 6.--Water-scorpion (_Nepa cinerea_) with raptorial
fore-legs, heteropterous wings, and long siphon for conveying air to
spiracles. Somewhat magnified. sc, scutellum; co, cl, m, corium, clavus
and membrane of forewing.]
[Illustration: From Marlatt, _Bull._ 14 (N.S.) _Div. Ent. U.S. Dept.
Agr._
FIG. 7.
a, Body of male Cicad from below, showing cover-plates of musical
organs;
b, From above showing drums, natural size;
c, Section showing muscles which vibrate drum (magnified);
d, A drum at rest;
e, Thrown into vibration, more highly magnified.]
_Sound-producing Organs._--The Hemiptera are remarkable for the variety
of their stridulating organs. In many genera of the _Pentatomidae_,
bristle-bearing tubercles on the legs are scraped across a set of fine
striations on the abdominal sterna. In _Halobates_ a comb-like series of
sharp spines on the fore-shin can be drawn across a set of blunt
processes on the shin of the opposite leg. Males of the little
water-bugs of the genus _Corixa_ make a shrill chirping note by drawing
a row of teeth on the flattened fore-foot across a group of spines on
the haunch of the opposite leg. But the loudest and most remarkable
vocal organs of all insects are those of the male cicads, which "sing"
by the rapid vibration of a pair of "drums" or membranes within the
metathorax. These drums are worked by special muscles, and the cavities
in which they lie are protected by conspicuous plates visible beneath
the base of the abdomen (see fig. 7).
_Fossil History._--The Heteroptera can be traced back farther than any
other winged insects if the fossil _Protocimex silurica_ Moberg, from
the Ordovician slates of Sweden is rightly regarded as the wing of a
bug. But according to the recent researches of A. Handlirsch it is not
insectan at all. Both Heteropterous and Homopterous genera have been
described from the Carboniferous, but the true nature of some of these
is doubtful. _Eugereon_ is a remarkable Permian fossil, with jaws that
are typically hemipterous except that the second maxillae are not fused
and with cockroach-like wings. In the Jurassic period many of the
existing families, such as the _Cicadidae_, _Fulgoridae_, _Aphidae_,
_Nepidae_, _Reduviidae_, _Hydrometridae_, _Lygaeidae_ and _Coreidae_,
had already become differentiated.
_Classification._--The number of described species of Hemiptera must
now be nearly 20,000. The order is divided into two sub-orders, the
Heteroptera and the Homoptera. The Anoplura or lice should not be
included among the Hemiptera, but it has been thought convenient to
refer briefly to them at the close of this article.
HETEROPTERA