HYDROGEN 



175 



HYDROZOA 



tact with hot iron into hydrogen and oxygen, 

 and that the hydrogen explodes. 

 Hydrogen type=Hydrochloric type: the type 

 of chemical combination, of which the for- 

 mation of hydrochloric acid is an example: 

 includes all the metals, aldehydes, ketones, 

 and hydrocarbons. 



Hydrogenium, (hi-dro-jen'i-um). [Hydrogen, 

 q.v. Gk. gennao, I produce.] The hypo- 

 thetical metal of which hydrogen is supposed 

 to be the vapour. 



Hydrographical, (hi-dro-grafi-kal). [Hydro, 

 q.v.; Gk. grapho, I write.] Connected with, 

 or relating to, hydrography. 

 Hydrography, (hl-drog'ra-fi). [Hydro, q.v. ; 

 Gk. grapho, I write.] The measurement and 

 description of large bodies of water, as the 

 sea, rivers, lakes, &c. 



Hydroid, (hi'droid). [Hydra, q.v. ; Gk. eidos, 

 form.] Connected with, or resembling hy- 

 drae. H. Zoophytes: those which secrete 

 coral=Hydroida: the early form of medusas 

 and jelly-fishes. 



Hydroida, ( hi-droi'da ). [Hydra, q.v.; Gk. 

 eidos, form.] A primary division of Hydrozoa, 

 mostly compound, and usually fixed to some 

 foreign body, usually in a horny sheath. , 

 Hydrokinetics. v. Kinetics. 

 HydroleaceaB=HydrophyllacesB, q. v. 

 Hydroleic acid, (hi-drol'e-ik). [Hydro and 



Oleic, q.v.} v. Oleic acid. 

 Hydrolite, ( hi'dro-lit ). [Hydro, q.v.; Gk. 

 lithos, stone.] A mineral; also called Gme- 

 linite, q.v. 



Hydromagnesite, (hi-dro-mag'ne-sit). [Hydro 

 and Magnesium, q.v.] A mineral, belonging 

 to the calcite group. 



Hydromellonic acid (hi-dr5-mel-lon'ik). [Hy- 

 dro and Mellon, q. v.^HsCgN^: a substance 

 compounded of hydrogen and mellon. 

 Hydrometer, ( hi-drom'e-ter ). [Hydro and 

 Meter, q.v.] An instrument to determine 

 specific gravity by the measurement of the 

 weight of a volume of water equal to the 

 volume of the given su bstance. 

 Hydrometrica, ( hi-dro-met'ri-ka ). [Hydro, 

 g.v.]=Funaria hydrometrica=Cord moss, an 

 Urn-moss. 



Eydrometridae, ( hi-dro-met'ri-dC ). [Hydro 

 and Meter, q.v. ; Gk. eidos, for m.]= Water 

 gnats ; a family of insects, belonging to He- 

 teroptera. 



Hydropeltidese, (hl-dro-pel-tid'e-S). [Hydro, 

 q.v. ; Gk. pelte, shield.] = Hydropeltuliuese, 

 q.v. 



HydropeltidineiB, (hi-dro-pel-ti-din'e-5). [Hy- 

 dro, q.v.: Gk. pelte, shield.]=Water-shields: 

 aquatic plants, with solitary flowers=Cabom- 

 bacese, q.v. 



Hydrophane, (hi'dro-fan). [Hydro, q.v. ; Gk. 

 phaino, I appear.] A variety of opal, which 

 becomes ti-anslucent in water. 

 Hydrophidae, (hi-drofi-de). [Hydrophis, the 

 typical genus. ]= Water snakes : a family of 

 venomous serpents, v. Ophidia. 

 Hydrophora, (hi-drof'o-ra). [Hydra, q.v. ; Gk. 

 phoreo, I bear.] A primary division of Hy- 

 drozoa; have numerous tentacles; form, by 

 budding, free swimming zoids, 



Hydrophyllacese, (hi-dro-fil-la'se-e). [Hydro- 

 phyllum, q.v.] = Hydrophyls : American 

 plants, with rough leaves and gay flowers, 

 forming a division of Cortusales. 



Hydrophyllum, (hi-dr5-fil'lum). [Hydro, q. v. ; 

 Gk. phyllon, leaf.]=Water-leaf : a plant the 

 type of Hydrophyllacese. 



Hydrophyta, (hi-drof'i-ta). [Hydro, q.v. ; Gk. 

 'phytos, plant.]=Algales, q.v. 



Hydropiper, (hi-dro'pi-per). [Hydro and Piper, 

 g.v.]=Elatine hydropiper= Water-pepper : a 

 plant belonging to Elatinacese. 



Hydropiperoin, (hi-dro-pip'er-oin). [Hydro- 

 piper, q.v.}=C\$LiQQ\ a substance obtained 

 from Hydropiper. 



Hydropotassic, (hl-drS-po-tas'ik). [Hydro and 

 Potassic, q.v.} H. salts: hydrated salts of 



_potas8ium. 



Hydroquinone, (hl-drS-kwi-non'). [Hydro and 

 Quinine, $.v.]=Arctuvin, q.v. 



Hydrorhiza, (hi-dro-ri'za). [Hydra, q.v.; Gk. 

 rkiza, root.] The adhering base of a Hydro- 

 zoon. 



Hydrosaurus, (hi-dro-saw'ms). [Hydro and 

 Sauria, q. v.] Lace-lizard: an animal belong- 

 ing to Iguanidffi. 



Hydroselenic, (hi-dr5-s5-len'ik). [Hydro and 

 Selenium, q.v.] v. Selenic. 



Hydrosoma, (hi-dro-so'ma). [Hydra, q.v. ; Gk. 

 soma, body.] The entire body of a hydro- 

 zoon, whether simple, as in Hydra, or com- 

 pound, as in Sertularia. 



Hydrostatics, (hl-dro-stat'iks). [Hydro and 

 Statics, q.v.] The science of forces that are 

 in equilibrium in liquids. H. arch: an arch 

 adapted to support the pressure of a body of 

 water. H. balance: an instrument to deter- 

 mine the specific gravity of a solid body or 

 of a liquid. H. paradox, v. Paradox. 



Hydrosulphates, (hl-dro-sulf ats). [Hydro and 

 Sulphates, q.v.] Compounds of hydrosul- 

 phuric acid with bases. 



Hydrosulphocyanic acid=HCyS: a compound 

 of hydrogen, sulphur, and cyanogen: an 

 odorous, oily, poisonous liquid. 



Hydrosulphuric acid, (hi-dro-sul-fu'rik). [Hy- 

 dro and Sulphuric, Q.v.]=H 2 S=Dihydric= 

 Sulphuretted hydrogen : a colourless, poison- 

 ous gas, with strong disagreeable odour 



Hydrotheca, (hi-dro-the'ka). [Hydra, q.v.: 

 Gk.thcka, case.] Little cup-like expansions, 

 in compound hydrozoa, into which polypitea 

 fit. 



Hydrothermal, (hi-dro-ther'mal). [Hydro and 

 Thermal, q.v.] Relating to the action of 

 heated water. 



Hydrotic acid, (hI-drot'ik)=Sudoric acid. 



Hydrous, (hi'drus). [Hydra, q.v.] An insect 

 belonging to Hydrophilidsa. //. piceus= 

 Black water-beetle. 



Hydroxyl, (hi-droks'il). [Hydro and Oxygen, 

 g.v.]:=H 2 O2=Peroxide of hydrogen =Hydrio 

 dioxide: "a colourless bleaching liquid easily 

 decomposed. 



Hydroxylamine, ( hl-droks-il'a-mm ). [Hy- 

 droxyl and Amine, g.v.]=NHzO: a volatile 

 base, known only in solution. 



Hydrozoa, (hl-drO-zo'a). [Hydra, q.v.; Gk. 

 20cm, animal.] Jelly-fishes, sea-firs, &c. : 



