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Helicotrema

The opening by which the two scalae communicate at the top of the cochlea of the ear.

Heliocentrical Heliocentric

pertaining to the sun's center, or appearing to be seen from it; having, or relating to, the sun as a center; -- opposed to geocentrical.

Heliogram

A message transmitted by a heliograph.

Heliograph

To telegraph, or signal, with a heliograph.

Heliolite

A fossil coral of the genus Heliolites, having twelve-rayed cells. It is found in the Silurian rocks.

Heliometer

An instrument devised originally for measuring the diameter of the sun; now employed for delicate measurements of the distance and relative direction of two stars too far apart to be easily measured in the field of view of an ordinary telescope.

Heliometry

The apart or practice of measuring the diameters of heavenly bodies, their relative distances, etc. See Heliometer.

Heliopora

An East Indian stony coral now known to belong to the Alcyonaria; -- called also blue coral.

Helioscope

A telescope or instrument for viewing the sun without injury to the eyes, as through colored glasses, or with mirrors which reflect but a small portion of light.

Heliostat

An instrument consisting of a mirror moved by clockwork, by which a sunbeam is made apparently stationary, by being steadily directed to one spot during the whole of its diurnal period; also, a geodetic heliotrope.

Heliotrope

An instrument or machine for showing when the sun arrived at the tropics and equinoctial line.

Heliotroper

The person at a geodetic station who has charge of the heliotrope.

Heliotropic

Manifesting heliotropism; turning toward the sun.

Heliotropism

The phenomenon of turning toward the light, seen in many leaves and flowers.

Heliotype

A picture obtained by the process of heliotypy.

Heliotypy

A method of transferring pictures from photographic negatives to hardened gelatin plates from which impressions are produced on paper as by lithography.

Heliozoa

An order of fresh-water rhizopods having a more or less globular form, with slender radiating pseudopodia; the sun animalcule.

Helipterum

genus of South African and Australian herbs or shrubs grown as everlastings; the various Helipterum species are currently in process of being assigned to other genera, especially Pteropogon and Hyalosperma.

Helium

An inert, monoatomic, gaseous element occurring in the atmosphere of the sun and stars, and in small quantities in the earth's atmosphere, in several minerals and in certain mineral waters. It is obtained from natural gas in industrial quantities. Symbol, He; atomic number 2; at. wt., 4.0026 (C=12.011). Helium was first detected spectroscopically in the sun by Lockyer in 1868; it was first prepared by Ramsay in 1895. Helium has a density of 1.98 compared with hydrogen, and is more difficult to liquefy than the latter. Chemically, it is an inert noble gas, belonging to the argon group, and cannot be made to form compounds. The helium nucleus is the charged particle which constitutes alpha rays, and helium is therefore formed as a decomposition product of certain radioactive substances such as radium. The normal helium nucleus has two protons and two neutrons, but an isotope with only one neutron is also observed in atmospheric helium at an abundance of 0.013 %. Liquid helium has a boiling point of -268.9/ C at atmospheric pressure, and is used for maintaining very low temperatures, both in laboratory experimentation and in commercial applications to maintain superconductivity in low-temperature superconducting devices. Gaseous helium at normal temperatures is used for buoyancy in blimps, dirigibles, and high-altitude balloons, and also for amusement in party balloons.

Helix

A nonplane curve whose tangents are all equally inclined to a given plane. The common helix is the curve formed by the thread of the ordinary screw. It is distinguished from the spiral, all the convolutions of which are in the plane.

hell-bent

recklessly determined; as, hell-bent on winning.

Hellbender

A large North American aquatic salamander (Protonopsis horrida or Menopoma Alleghaniensis). It is very voracious and very tenacious of life. Also called alligator, and water dog.

Hellbroth

A composition for infernal purposes; a magical preparation.

Helleborein

A poisonous glucoside accompanying helleborin in several species of hellebore, and extracted as a white crystalline substance with a bittersweet taste. It has a strong action on the heart, resembling digitalin.

Helleborin

A poisonous glucoside found in several species of hellebore, and extracted as a white crystalline substance with a sharp tingling taste. It possesses the essential virtues of the plant; -- called also elleborin.

Helleborism

The practice or theory of using hellebore as a medicine.

Hellene

A native of either ancient or modern Greece; a Greek.

Hellenian

Of or pertaining to the Hellenes, or Greeks.

Hellenic

The dialect, formed with slight variations from the Attic, which prevailed among Greek writers after the time of Alexander.

Hellenism

A phrase or form of speech in accordance with genius and construction or idioms of the Greek language; a Grecism.

Hellenist

One who affiliates with Greeks, or imitates Greek manners; esp., a person of Jewish extraction who used the Greek language as his mother tongue, as did the Jews of Asia Minor, Greece, Syria, and Egypt; distinguished from the Hebraists, or native Jews (Acts vi. 1).

Hellenize

To give a Greek form or character to; to Grecize; as, to Hellenize a word.

Hellespont

A narrow strait between Europe and Asia, now called the Daradanelles. It connects the Aegean Sea and the sea of Marmora.

Hellgramite Hellgamite

The aquatic larva of a large American winged insect (Corydalus cornutus), much used a fish bait by anglers; the dobson. It belongs to the Neuroptera.

Hellier

One who heles or covers; hence, a tiler, slater, or thatcher.

Hellish

Of or pertaining to hell; like hell; infernal; malignant; wicked; detestable; diabolical.

Hello

An exclamation used as a greeting, to call attention, as an exclamation of surprise, or to encourage one. This variant of Halloo and Holloo has become the dominant form. In the United States, it is the most common greeting used in answering a telephone.

Helm

To cover or furnish with a helm or helmet.

Helmet

A defensive covering for the head. See Casque, Headpiece, Morion, Sallet, and Illust. of Beaver.

Helmet-shaped

Shaped like a helmet; galeate. See Illust. of Galeate.

Helmeted

Wearing a helmet; furnished with or having a helmet or helmet-shaped part; galeate.

Helminth

An intestinal worm, or wormlike intestinal parasite; one of the Helminthes.

Helminthes

One of the grand divisions or branches of the animal kingdom. It is a large group including a vast number of species, most of which are parasitic. Called also Enthelminthes, Enthelmintha.

Helminthiasis

A disease in which worms are present in some part of the body.

Helminthic

Of or relating to worms, or Helminthes; expelling worms. A vermifuge; an anthelmintic.

Helminthite

One of the sinuous tracks on the surfaces of many stones, and popularly considered as worm trails.

Helminthology

The natural history, or study, of worms, esp. parasitic worms.

Helmsman

The man at the helm; a steersman.

Helmwind

A wind attending or presaged by the cloud called helm.

Helodermatidae

A natural family of lizards, including the only known venomous lizards.

Helot

A slave in ancient Sparta; a Spartan serf; hence, a slave or serf.

Helotism

The condition of the Helots or slaves in Sparta; slavery.

Helotium

The type genus of the Helotiaceae.

Helotry

The Helots, collectively; slaves; bondsmen.

Help

To lend aid or assistance; to contribute strength or means; to avail or be of use; to assist.

Helper

One who, or that which, helps, aids, assists, or relieves; as, a lay helper in a parish.

Helpful

Furnishing help; giving aid; assistant; useful; salutary.

helping

a quantity of food served as part of a meal.

Helpless

Destitute of help or strength; unable to help or defend one's self; needing help; feeble; weak; as, a helpless infant.

Helpmate

A helper; a companion; specifically, a wife.

Helter-skelter

In hurry and confusion; without definite purpose; irregularly.

Helve

To furnish with a helve, as an ax.

Helvetian

Same as Helvetic. A Swiss; a Switzer.

Helvetic

Of or pertaining to the Helvetii, the ancient inhabitant of the Alps, now Switzerland, or to the modern states and inhabitant of the Alpine regions; as, the Helvetic confederacy; Helvetic states.

Helvite Helvine

A mineral of a yellowish color, consisting chiefly of silica, glucina, manganese, and iron, with a little sulphur.

Helxine

A genus of plants consisting of one species; a dwarf creeping mat-forming evergreen herb.

Hem

To form a hem or border to; to fold and sew down the edge of.

Hemachate

A species of agate, sprinkled with spots of red jasper.

Hemacite

A composition made from blood, mixed with mineral or vegetable substances, used for making buttons, door knobs, etc.

Hemadynamics

The principles of dynamics in their application to the blood; that part of science which treats of the motion of the blood.

Hemadynamometer

An instrument by which the pressure of the blood in the arteries, or veins, is measured by the height to which it will raise a column of mercury; -- called also a haemomanometer.

Hemal

Relating to the blood or blood vessels; pertaining to, situated in the region of, or on the side with, the heart and great blood vessels; -- opposed to neural.

Hemapophysis

The second element in each half of a hemal arch, corresponding to the sternal part of a rib.

Hemastatics

Laws relating to the equilibrium of the blood in the blood vessels.

Hematein

A reddish brown or violet crystalline substance, C16H12O6, got from hematoxylin by partial oxidation, and regarded as analogous to the phthaleins.

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