Hydrosaunis 
genus of monitor-lizards, of the family Mo- 
nitorida? or Vnranidue: so named from their 
aquatic habits. H. salvator, the water-monitor, is 
said to attain a length of 8 feet; it inhabits India and 
the Malay peninsula, and is known there as the kabara- 
goya. An Australian species, //. giyanteu*, is known as 
the lace-lizard. 
hydroscope (hl'dro-skop), n. [= F. hydroscope 
= Pg. hydroscopo = It. idroscopo, < Gr. vdpaoKo- 
mov, a water-clock (cf . vdpoanmof, seeking or 
finding water), < vfiup (ifp-), water, + OKOVCIV, 
view.] 1. A kind of water-clock or instrument 
formerly used for measuring time, consisting of 
a cylindrical graduated tube, from which water 
slowly escaped through an aperture in the coni- 
cal bottom, the subsidence of the water mark- 
ing the lapse of time. 2. A hygroscope. 
hydroselenate (hi-dro-sel'e-nat), n. [< hydro- 
selen-ic + -ate 1 .'] In chem., a salt formed by the 
union of hydroselenic acid with a salinable base. 
Also called selenide. 
hydroselenic (hi'dro-se-len'ik), a. [< hydro- 
(gen) + selen(ium) 4- -ic.] Of or pertaining to 
a combination of hydrogen and selenium. Hy- 
droselenic acid, HgSe, a colorless gas which resembles 
sulphureted hydrogen, but is much more offensive. Also 
called seleniureted hydrogen, 
hydrosoma (hl-dro-so'ma). n. [NL., < Gr. iiSup 
(vip-), water, + au'fia, body.] 1. Pl.hydrosomata 
(-ma-ta). The entire body of a hydrozoan, usu- 
ally" compounded of several hydranths. Also 
hydrosome. 
In an early stage . . . every hydrozoon is represented 
by a single hydranth, . . . but, in many cases, the buds 
developed from the primary hydranth remain connected 
together by a common stem or ccenosarc, and thus give rise 
to a compound body, or hydrosoma. 
Uuxley, Anat. Invert, p. 117. 
2. [cap.] In entom., same as Bydrophiliig. La- 
porte, 1840. 
hydrosomal (hi-dro-so'mal), a. [< hydrosoma 
T -al.] Of or pertaining to a hydrosoma : as, 
a hydrosomal expansion; a hydrosomal layer. 
See extract under Millepora. Also hydrosoma- 
tous. 
hydrosomata, . Plural of hydrosoma, 1. 
hydrosomatous (hi-dro-som'a-tus), o. Same 
as hydroxomal. 
hydrosome (hi'dro-som), n. [< NL. hydrosoma. ] 
Same as hydrosoma, 1. 
hydrosphere (hi'dro-sfer), n. [< Gr. Map (Mp-), 
water, + a<palpa, sphere.] The aqueous envelop 
of the globe. The term is used in contradistinction to 
atmosphere, to designate the moisture which the atmo- 
sphere always contains, and which therefore surrounds 
the globe, just as the atmosphere Itself does. [Rare.] 
hydrospire (hi'dro-spir), . [< Gr. v6up(vip-), 
water, + avslpa, a coil, a spire. ] One of a sys- 
tem of lamellar tubes which lie between and 
below the ambulacra of some crinoids, sup- 
posed to have been connected with the respir- 
atory function. 
Pores on the antamhulacral surface may be, ... as in 
Pseudocrinus, Echinoencrinus and other genera, slit-like, 
and arranged to form pectinated rhombs or hydrospireg, 
the two halves of each rhomb being on separate plates. 
Xneyc. Brit., VII. 688. 
Hydrostachydese (hi'dro-sta-kid'e-e), n. pi. 
[NL. (S. de Jussieu), < tlydrostacftys (-yd-) + 
-eat.] A tribe of dicotyledonous apetalous 
plants, of the natural order Podostemaceai, con- 
taining the single genus Hydrostacliys. Also 
HydrostachyetE. 
Hydrostacliys (h5-dros'ta-kis), . [NL. (Du- 
petit Thouars), < Gr. i<6up (i>Sp-). water, + oraxvf, 
an ear of corn.] A small genus of aquatic herbs, 
of the natural order Podostemacece, the type of 
the tribe Hydrostachydeie. It has dioecious flowers 
in dense spikes; the flowers naked; the male with 1 sta- 
men, the female with a 1-celled ovary and 2 parietal pla- 
centae ; stem tubular ; and leaves long, dilated at the base, 
and simply pinnatlfld or pinnatisected. About 9 species 
are known, natives of Madagascar and Africa. 
hydrostat (hi'dro-stat), n. [< Gr. Mpoordn/f, a 
hydrostatic balance : see hydrostatic.] 1. An 
apparatus of any kind for preventing the ex- 
plosion of steam-boilers. 2. An electrical 
device for detecting the presence of water, 
used as a protection against damage to build- 
ings from overflow or leakage. 
The first hydrostat I constructed consisted of two sets 
of conductors running at angles to each other, and sepa- 
rated by a material which would act as an insulator when 
dry and become a conductor when wet. 
Jour. Franklin Iitst., CXXVI. 331. 
hydrostatic (hi-dro-stat'ik), a. [= F. hydro- 
statique = Sp. hidrostdtico = Pg. hydrostatico = 
It. idrostatico, < NL. Jiydrostaticiis (NGr. Mpo- 
oramof), hydrostatic, < Gr. Mponrarrif, a hydro- 
static balance, < i&up (v&p-), water, + orarof, 
standing, ><mmKof, causing to stand: seestatic.] 
Pertaining to or in accordance with the priii- 
2940 
ciples of the equilibrium of fluids; relating to 
hydrostatics. Also hydrostatical Hydrostatic 
acalephs. See Hydrostatic^. Hydrostatic arch, a 
linear arch suited for sustaining at each point a normal 
pressure, proportional, like the pressure of a liquid in re- 
pose, to the depth below a given horizontal plane. Hy- 
drostatic balance, a balance used for determining ac- 
curately the specific gravity of bodies by weighing them 
in water. Hydrostatic bed. Same as water-bed. "Ry- 
drostatic bellows, an apparatus contrived to illustrate 
the law of the distribution of pressure through liquids, 
viz. that when any part of the surface of a confined liquid 
is pressed by any force, 
every part of the surface 
of the confining vessel 
equal in area to that part 
of the liquid is pressed by 
an equal force. It gen- 
erally consists of two cir- 
cular boards connected 
by leather fastened close- 
ly round their edges, as in 
an ordinary bellows, and 
having a small upright 
tube communicating 
with the interior. If a 
quantity of water is 
poured into the bellows, 
and a weight is placed 
upon the upper ooard, 
the water in the tube 
will rise above the level 
of the water in the bel- 
lows; but a point will 
hydroxid 
hydrotachylite (hl-dro-tak'i-15t), n. [< Gr. 
vdup (itip-), water, + E. tachylite.~\ A variety 
of tachylite containing as much as 15 per cent. 
of water. 
hydrotalcite (hi-dro-tal'sit), . [< Gr. v&up 
(i'6p-), water, + E. ialcite.] In mineral., same 
;is liouyliite. 
hydrotellurate (hi-dro-tel'u-rat), n. [< liyilro- 
tellnr(ic) + -ate 1 .] Iii chem., a salt formed by 
the combination of an acid composed of hydro- 
gen and tellurium with a salifiable base. 
hydrotelluric (hi"dro-te-lu'rik), a. [< hydro- 
(fli-n) + tellur(imu) 4- -ic.~] Of, pertaining to, 
or obtained from hydrogen and tellurium. 
hydrotheca (hi-dro-the'ka), .; pi. hydrotheco" 
(-se). [NL., (. Gr. i'&pixHinri, a reservoir of 
water, < Map (Up-), water, 4- Of/iai, a case, re- 
ceptacle: see Wieca.] In zool., a little chiti- 
nous cup in which each polypite of the Sertit- 
larida and Campanitlarida is protected ; a caly- 
cle. See cut under Campanularia. 
In many Hydrozoa, the ectoderm gives rise to a hard 
cuticular coating, and in 
Sertularidffi), this cuticular investment, on the hydranth, 
" 
some of these (I'ampanularidre, 
Hydrostatic Bellcws. 
funnel-mouthed tube : *, box with 
flexible sides: c, weight. 
be reached where (on ac- 
count of the above-men- 
tioned principle) the pressure caused by the weight of the 
smnll quantity of water in the tube will balance that of 
the water in the bellows and of the weight ; the higher the 
water in the tube the greater the weight that will be sus- 
tained by it. See hydraulic prew, under hydraulic. Hy- 
drostatic joint, a joint used for large water-mains, and 
consisting essentially of a ring of sheet-lead, which is 
driven into the bell of the pipe by pressure applied to a 
liquid in an annular space within the bell. The liquid 
commonly used is tar, and it is left in the pipe after the 
joint is closed. Hydrostatic paradox, the principle 
that any quantity of a perfect liquid, however small, may 
be made to balance any weight, however great. See hy- 
drostatic bellowt, above. Hydrostatic press. Same as 
hydraulic preat (which see, under hydraulic). Hydro- 
static weighing-machine, a machine operating upon 
the same hydrostatic principle as the hydrostatic bellows, 
which latter may be considered as such a machine. The 
weight of a body is indicated by or Inferred from the 
height of a column of distilled water, at a temperature 
of 4 C., which holds the body to be weighed In equilib- 
rium. 
Hydrostaticat (hi-dro-stat'i-ka), n. pi. [NL., 
neut. pi. of hydrostatieus : see hydrostatic.'] In 
Cuvier's system of classification, the second 
order of Acalepha, distinguished from the sim- 
ple acalephs by having one or more vessels 
filled with air, by means of which they suspend 
themselves in the water. The term is not now used ; 
the group corresponds to the Siphonophora or oceanic hy- 
drozoans, orders Physophora and Calycophora. 
hydrostatical (hl-dro-stat'i-kal), a. [< hydro- 
static + -al.] Same as hydrostatic. 
But this scarce evltable imperfection of hydrottatical 
and the like experiments does not hinder, but that by 
their help we may make good estimates of the weights 
and bulks of very many bodies. /;,,.//., Works, V. 466. 
hydrostatically (hl-dro-stat'i-kal-i), adv. Ac- 
cording to hydrostatics or to hydrostatic prin- 
ciples. 
hydrostatician (hi*dro-sta-tish'an), H. [< hy- 
drostatic + -ian. Cf. statician.] One who is 
versed in hydrostatics. 
It is known to hydrogtaticians that, according to a the- 
orem of Archimedes, the weight of a body belonging to 
that kind may be gathered from the weight of the water 
that is equal in magnitude to that part of the body that is 
immersed in that liquor, when the solid floats freely upon 
It. Boyle, Works, VI. 482. 
hydrostatics (hi-dro-stat'iks), n. [PI. of hy- 
drostatic: see -ics.] The mathematical theory 
of the pressure and equilibrium of incompres- 
sible fluids. 
hydrostomia (hl-dro-sto'mi-a), n. [NL., < Gr. 
vSup (i'dp-), water, + aro/ia, mouth.] Inpathol., 
excessive secretion of fluids into the mouth. 
The Lancet, No. 3413, p. 161. 
hydrosudopathy (hi"dro-su-dop'a-thi), n. [Ir- 
reg. < Gr. iidup (v6p-), water, + L. sudare, sweat 
(sudor, n., sweating), -I- Gr. waOof, suffering: 
see hydropathy.'] The treatment of diseases by 
cold water and sweating. 
hydrosulphid (hl-dro-sul'fid), . [< hydrr,(gen) 
+ milphid.] Same as sulphid. 
hydrosulphuret (hi-dro-sul'fu-ret), n. [< hy- 
dro(gen) + sttlphuret.] Same as sulphid OTSul- 
phuret. 
hydrosulphureted, hydrosulphuretted (hi- 
dro-sul'fu-ret-ed), a. [< hydrosulphuret + 
-erf 2 .] Combined with sulphureted hydrogen. 
hydrosulphurous (hi-dro-sul'fer-us), a. [< 
lii/dro(i/eH) + sulphur + -OMS.] Compounded 
of hydrogen and sulphur. Hydrosulphurous 
acidt, hyposulphurous acid, 
takes the shape of a case or "cell" the hydrotheca into 
which the hydranth may be more or less completely re- 
tri-ti-d. Huxley, Anat. Invert., p. 117. 
hydrothecal (hi-dro-the'kal), a. [< hydrotheca 
+ -al.] Having tlie character of hydrotheca; 
calycular. 
hydrotherapeutic (hl-dro-ther-a-pu'tik), o. 
[< Gr. iiiup (yip-), water, 4- E. therapeutic.] Of 
or pertaining to hydrotherapeutics: as, hydro- 
therapeutic treatment. 
hydrotherapeutics (hi-dro-ther-a-pu'tiks), n. 
[PI. of hydmtherapeiitic : see -ics.] The use of 
water in various ways and at various tempera- 
tures for therapeutic purposes. 
hydrotherapy (hl-dro-ther'a-pi), n. [= F. hy- 
arotherapie = 8p. hidroterapia, < Gr. itaup (iifp-), 
water, 4- Oepairtia, cure, < Bepaircveiv, cure.] 
Same as hydrotherapeutics. 
hydrothennal (hi-dro-ther'mal), a. [< Gr. 
v6ap (i'6p-), water, + dep/t6f, hot.^ Of or relat- 
ing to heated water : specifically applied to the 
action of heated waters in producing geological 
changes by dissolving mineral substances and 
redepositing them when cooled. 
hydrothorax (hi-dro-tho'raks), . [NL., < Gr. 
uiup (iilp-), water, 4- Qijpaf, the chest.] In pa- 
thol., the presence of serous fluid in one or 
both pleural cavities. 
hydrotict (hi-drot'ik), a. and n. [< F. hydro- 
tique, < Gr. txJpor^r, moisture, < iitiup (ioyj-), wa- 
ter.j I. a. Causing a discharge of water. 
II. n. In med., a nydragogue. 
hydroticalt (hi-drot'i-kal), . [< hydrotic + 
-<il.] Same as hydrotic. 
hydrotimeter (hi-dro-tim'e-ter),. [IrregXGr. 
vdportK, moisture, + '/icrpov, a measure.] An in- 
strument used in the determination of the hard- 
ness of Water. It consists of a tube so graduated that 
an alcoholic soap-solution of standard strength contained 
in 23 divisions of it shall give a permanent lather with 
40 cubic centimeters of a solution of calcium chlorid of 
standard strength. Each one of these divisions is called 
a degree, and In saying that " the water does not exceed 8 
degrees hydrotimeter, ' it is meant that not more than 8 
divisions of the standard soap-solution delivered from the 
hydrotimeter is necessary to make a permanent lather 
with 40 cubic centimeters of the water in question. 
hydrotitanite (hi-dro-ti'tan-It), n. [< Gr. 
i'6up (Up-), water, + "E. titanite, q. v.] A hy- 
drated alteration product of the perofskite of 
Magnet Cove in Arkansas. . 
hydrotrophe (hi'dro-trof ), n. [< Gr. Map (Mo-), 
water, + rptyetv, thicken, congeal, nourish.] 
An apparatus for raising water by means of 
condensing steam in chambers. It is similar 
in principle to the pulsometer, aquometer, etc. 
E. H. Knight. 
hydrotropic (hi-dro-trop'ik), a. [< Gr. vfup 
(i'ip-), water, -I- rpmof, a turn.] Pertaining to 
or affected by hydrotropism. 
hydrotropisM (hi-drot'ro-pizm), )(. [As hydro- 
troj>-ic + -ism.] A state induced in a growing 
organ by the influence of moisture, in which 
under certain conditions it turns toward the 
moisture, and under other little understood 
conditions it turns away from the moisture. 
Organs which curve so as to apply themselves to the moist 
surfaces are termed positively hydrotropic; those which 
are induced to curve away from the dampness are termed 
negatively hydrotropif. 
hydrous (hi'drus), a. [< Gr. Mup (Up-), water, 
T -ous.] 1. Containing water; watery. 2. 
Containing hydrogen. 
hydroxid, hydroxide (hi-drok'sid, -sid or -sid), 
n. [< Gr. idup (Up-), water, + E. oxid.] A me- 
tallic or basic radical combined with one or 
