Imágenes de páginas
PDF

boiling. It then becomes brittle, the gelatine being the principal cause of its suppleness and toughness. From some experiments by Mr. Hatchett, it is inferred that the hair which loses its curl in moist weather, and which is softest and most flexible, is that which yields its gelatine most readily; whereas strong and elastic hair yields it with the greatest difficulty, and in the smallest proportion. By an experiment of Berthollet's, 1,152 parts of hair yielded

Carbonate of ammonia 90

Water 179

Oil 488

Gases 271

Coal 3«4

1152

The oil was soluble in alcohol, burnt with brilliancy, and with scintillations like the hair itself. The coal was attracted by the magnet, which proves it contains iron. The alkalies, at a boiling heat, dissolve hair, and form- with it an animal soap. Sulphuric acid dissolves hair, with the aid of heat. Hair is usually distinguished into various kinds: the stiffest and strongest is called bristles, such as that on the backs of swine. When remarkably soft and pliable, it is denominated wool, as that on sheep; and the finest of all, is called down. From wool more than half its weight of oxalic acid is obtained. Feathers possess similar properties to those of hair; the quill is composed of coagulated albumen, but no gelatine. Muriatic acid dissolves hair, and the solution is very like a solution of glue in the same acid. When plunged into acid, in the state of gas, it is very soon converted into a pulp.

Hair, or Down, of plants, a general term, expressive of all the hairy and glandular appearances on the surface of plants, to which they are supposed by naturalists to serve the double purpose of defensive weapons and vessels of secretion. These hairs are minute threads, of greater or less length and solidity, some of them visible to the naked eye, whilst others are rendered visible only by the help of glasses. Examined by a microscope, almost all the parts of plants, particularly the young stalks or stems, appear covered with hairs. Hairs on the surface of plants, present themselves under various forms; in the leguminous plants, they are generally cylindi ic; in the mallow tribe, terminated in a point; in agrimony, shaped like a fish-hook; in nettle, awl-shaped and jointed; and in some

compound flowers, with hollow of funnelshaped florets, they are terminated in two crooked points.

Hair's breadth, a measure of length, being the forty-eighth part of an inch.

HAKE, in ichthyology, the English name of the gadus, with two fins on the back, and the underjaw longest. It grows to two feet or more in length, but is the slenderest of all the gadi. See Gadus.

HALBARD, or Halbkrt, in the art of war, a well-known weapon, carried by the Serjeants of foot and dragoons. It is a sort of spear, the shaft of which is about five feet long, and made of ash or other wood. Its head is armed with a steel point, edged on both sides, not unlike the point of a twoedged sword: but besides this sharp point, which is in a line with the shaft, there is a cross piece of steel, flat and pointed at both ends; but generally with a cutting edge at one extremity, and a bent sharp point at the other; so that it serves equally to cut down, or push withal. It is also useful in determining the ground between the ranks, and in adjusting the files of a battalion.

HALE, in the sea langauge, signifies pull; as to hale up is to pull up; to hale in or out, is.to pull in or out To over-hale a rope, is to hale it too stiff, or to hale it the contrary way.

HALES (stephen), D. D. in biography, an eminent natural philosopher and excellent parish clergyman, was sixth son of Thomas Hales, Esq. of Beckesbourn, in Kent, where he was born in 1677. At the age of nineteen he was entered a pensioner of Bene't College, Cambridge, of which he was elected a fellow iu 1702. He afterwards proceeded M. A. and entered into holy orders. During his residence at Cambridge he distinguished himself by his diligent researches into various branches of natural knowledge, particularly botany and anatomy. In these studies he had for an associate William Slukcley, afterwards M. D. and an eminent antiquary. A turn of novel and ingenious experiments, and of mechanical inventions, early characterized Mr. Hales, and a contrivance for obtaining a preparation of the lungs in lead with the construction of a planetarium upon the Newtonian system of astronomy, are mentioned among the products of his skill at this period. In 1710 he was presented to the perpetual curacy of Teddington, in Middlesex. Not long after he vacated his fellowship by accepting the living of Portlock, in Somersetshire, which he exchanged for that of Farringdon, in Hampshire. He then married the daughter of a clergyman, who died after two years, leaving no issue. Henceforth he lived entirely as a single man, devoting himself entirely to science, and objects of public utility. In 1717 he was elected a member of the Royal Society, and in the following year he read before that body an account of some experiments concerning the effect of the sun's h< at in raising the sap in vegetables. The farther prosecution of these experiments gave rise to an excellent work published in 1727, entitled " Vegetable Statics, or an account of some statical Experiments on the Sap of Vegetables; being an Essay towards a Natural History of Vegetation: also, a Specimen of an Attempt to Analyse the Air by a variety of Chemico-Statiral Experiments, which were read at several Meetings before the Royal Society," 8vo. This piece is justly esteemed a model of experimental investigation. Haller characterizes it as " liber eximus, cujus paucissimos babemus semulos qui toties potius legi volet, quam decerpi." It begins by ascertaining the vast quantity of watery humour perspired by plants, sometimes equalling their whole weight in a single day. It then specifies the power with which they attract the nutritious juice through their capillary tubes, and considers the lateral motion of this juice from trunk to branches, and vice versa. It disproves any proper circulation of this fluid, but establishes its ascent during the day, and descent during the night. The leaves are proved to be inspiratory organs, both of air and water. There are besides a number of curious remarks upon the vegetable system, as well as upon the constitution of atmospherical air, into which he was one of the experimental enquirers. His experiments upon air relate indeed solely to its generation and absorption, its elastic and non-elastic states, and do not proceed to the discovery of any of those species of air or gases which have so much engaged the attention of modern philosophers, though they manifestly led to such discoveries. A second edition of this work appeared in 1731, and in 1733 he published, as a kind of sequel to it, his " Statical Essays, containing Hxmastatics; or an Account of some Hydraulic and Hydrostatical Experiments made on the Blood and Bloodvessels of Animals: also, an Account of Mme Experiments on Stones in the Kidneys and Bladder, Sec." In this he discussed some fundamental points relative to physio

logy, as the force and celerity with which the blood is propelled in the arteries, its retardation in the capillary vessels, the area of the heart, and the weight of blood sustained by it, the effects of respiration, and the alteration of air by breathing, &c. His enquiries concerning the urinary calculus relates to its chemical composition, and to the means of dissolving it; of which, suggested by Lim, is fixed air, or that produced by sulphuric acid and fixed alkali in a state of effervescence. He also proposes injections into the bladder, and gives a contrivance for that purpose. This subject he afterwards pursued more particularly, and published an account of some experiments on Mrs. Stephens's celebrated medicines, in 1740. The reputation of this worthy man, kept pace with his useful labours. In 1732 he was appointed one of the trustees for settling a colony in Georgia; and, in 173S, the University of Oxford presented him with the degree of D. D. He performed a valuable service to the health and morals of the poor, by printing, anonimously, " A Friendly Admonition to the Drinkers of Gin, Brandy,and other Spirituous Liquors," which has been several times reprinted and distributed gratis. In 1739 he printed "Philosophical Experiments on Sea Water, Corn, Flesh, and other Substances," 8vo. chiefly intended for the use of navigators. A paper on a similar subject, and the solution of the stone in the bladder obtained him, in the same year, the gold medal from the Royal Society. One of the most useful of Dr. Hales' invention was that of ventilators for renewing the air in mines, prisons, hospitals, and holds of ships, which he disclosed to the Royal Society in 1741. Some years afterwards his machines were fixed on the Savoy and Newgate Prisons, to the great benefit of the persons confined in them, among whom the progress of the gaolfever was much diminished. His plans for producing a free circulation of air were also applied by him for the cleansing and preservation of corn: for the former purpose he invented a machine called a backheaver, which he described in the Gentleman's Magazine for 1745 and 1747. His attention to medical subjects was farther evinced, by a paper read before the Royal Society, in describing a method for conveying liquors into the abdomen after tapping; by some experiments and observations on tar-water; and a detection of some fallacious boasts concerning the efficacy of a lithontriptic, called the liquid shell. A sermon, which he preached before the College of Physicians, in 1751, on Dr. Crown's foundation, contains some curious physiological remarks relative to the benevolence of the Deity, as displayed in the human frame. His literary honours were augmented in 17 .VI. by his election as a foreign member of the French Academy of Sciences, in the room of Sir Hans Sloane.

Dr. Hales, though he spent his time in retirement atTeddington, was not unknown to many persons of rank, whom he visited and received at his house with all the simplicity of his modest and unaffected character. Frederick, Prince of Wales, honoured himself with frequent calls upon the philosopher, his neighbour, whom he delighted to surprise in his experimental researches. At the death of that prince he was, without any solicitation, made clerk of the closet to the Princess Dowager. It was hinted to him that there was an intention of presenting him to the canonry of Windsor; but he desired to be excused accepting a promotion, which might have brought with it obligations of spending his time, interfering with the plan which for so many years he had adopted. His parochial duties, and the uninterrupted pursuit of his useful studies, continued to occupy him to an advanced period of life, during which he was never forsaken by his habitual cheerfulness and serenity of mind, sustained by temperance, piety, and conscious worth. He seems to have passed through life without an enemy, and perhaps the annals of biography cannot produce a character more marked by the union of blamelessness with active benevolence. Pope has recorded "Plain Parson Hales" as his model of sincere piety. Haller describes him as "pious, modest, indefatigable, and born for the discovery of truth." He died at Teddington, in January, 1761, in his eightyfourth year, and was buried under the tower of the church which he had rebuilt at his own expence. The Princess of Wales erected a monument to him in Westminster Abbey, in the Latin inscription of which the reader will be surprised to find nothing recorded of him but that he was her chaplain. But the reception his works met with throughout Europe, into the principal languages of which they were translated, will sufficiently perpetuate his fame as a philosopher.

HALESIA, in botany, so named in honour of the learned and venerable Stephen

Hales, D. D. F. R. S. a genus of the Bode- candria Monogyuia class and order. Natural order of Bicornes. Goajacanx, Jus sieu. Essential character: calyx fourtoothed, superior; corolla four-cleft; nut quadrangular, with two seeds. There are two species, viz. H. tetraptera, four-winged halesia, or snow-drop tree; and H. diptera, two-winged halesia.

HALF mark, a noble, or six shillings and eightpence.

Half moon, in fortification, an outwork composed of two faces, forming a salient angle, whose gorge is in form of a crescent, or half-moon: whence the name.

HALIOTIS, in natural history, the earshell. Animal a limax: shell univalve, dilated, ear-shaped, with a longitudinal row of orifices along the surface; spire1 lateral, and almost concealed. There are nineteen species, of which H. tuberculata is described by Mr. Donovan as a native of this country. The shell is subovate, the outside transversely grooved, rugged, and tuberculate. The inside is like mother-ofpearl. It inhabits the sea near Guernsey, and is likewise frequently cast up on the southern shores of Devonshire. When living it adheres to rocks. According to Pennant this was the sea-ear of Aristotle.

HALL, in architecture, a large room at the entrance of a fine house and palace.

Hall is also a public building or court of justice, as Westminster-hall, Guild-hall, a company's hall, &c. In Westminster-hall are held the Courts of King's Bench, Common Pleas, Chancery, and Exchequer.

HALLERIA, in botany, so called from the famous Albert Haller, a genus of the Didynamia Angiospermia class and order. Natural order of Personatae. Scrophularix, Jus-ieu. Essential character: calyx trifid; corolla quadrifid; filaments longer than the corolla; berry inferior, two-celled. There is but one species, viz. H. lucida, African fly-honeysuckle, a native of the Cape.

HALLIARDS, in sea language, the ropes or tackles usually employed to hoist or lower any sail upon its respective masts or stay.

HALO, in physiology, a meteor in the form of a luminous ring or circle, of various colours, appearing round the bodies of the sun, moon, or stars. See Meteorology.

HALORAGIS, in botany, a genus of the Octaodria Tetragynia class and order. Natural order of Calycaullicma;. Onagra Jussieu. Essential character: calyx fourcleft, superior; petals four; drupe dry, inclosing a four-celled nut. There are two species, my.. H. prostraU and H. cercodia.

HAMAMELIS, in botany, a genus of the Tetrandria Digynia class and order. Natural order of Berberides, Jussieu. Essential character: involucre three-leaved; perianthers four-leaved; petals four; not two-horned, two-celled. There is only one species, viz. H. virginica, witch hazel.

HAMELIA, in botany, so called from Jean Baptiste du Hamel du Moncean, a genus of the Pentandria Monogynia class and order. Natural order of Rubiaceae, Jussieu. Essential character: corolla five, cleft; berry five-celled, inferior, manyseeded. There are four species, all natives of the West Indies.

HAMMER, a well known tool used by mechanics, consisting of an iron head, fixed crosswise upon a handle of wood.

There are several sorts of hammers used by blacksmiths; as, l. The hand-bammer, which is of such weight that it may be wielded or governed with one hand at the anvil. 2. The up-hand sledge, used with both hands, and seldom lifted above the head. 3. The about-sledge, which is the biggest hammer of all, and held by both hands at the farthest end of the handle, and being swung at arms-length over the head, is made to fall upon the work with as heavy a blow as possible. There is also another hammer used by smiths, called a rivettinghammer, which is the smallest of all, and is seldom used at the forge, unless upon small work.

HAMMOCK, in naval affairs, a piece of hempen cloth six feet long and three feet wide, gathered together at the two ends by means of a clue, and slung horizontally under the deck, forming a receptacle for a bed. There are about from fourteen to twenty inches in breadth allowed between the decks for every hammock in a ship of war. In preparing for battle, the hammocks, with their contents, are all firmly corded, taken upon deck, and fixed in various nettings, so as to form a barricade against small shot.

HAMSTER. See Muir.

HANAPER office, in the Court of Chancery, is that out of which all original writs issue that pass under the great seal, and all commissions of charitable uses, sewers, bankrupts, idiocy, lunacy, and the like. These writs, relating to the business of the subject, and the returns to them, were ori.

ginally kept in a hamper, in hanaperinl the other writs, relating to such matters wherein the crown is immediately or mediately concerned, were preserved in a little sack or bag, in porta baga; and thence arises the distinction of the hanaper office, and petty bag office; both of which belong to the common law court in Chancery

HAND. See Anatomy.

Hand breadth, a measure of three inches. By this standard the height of horses is estimated.

Hand cuffs, an instrument formed of two circular pieces of iron, each fixed on a hinge on the ends of a very short iron bar, which being locked over the wrists of a malefactor, prevents his using his hands.

Hand spikes, wooden levers used at sea to traverse the ordnance, or to turn the windlass in weighing up the anchor, &c. They are more commodious than iron crows, because their length allows a better poize.

Hands, in heraldry, are borne in coatarmour dexter and sinister, that is, rightand left, expanded or open. These are the most necessary parts of the human body, as they serve to express all sorts of actions, and even our very thoughts and designs; thus joining of hands is an universal token of friendship, and clapping of hands a general mark of applause.

HANKS, in naval affairs, are wooden rings fixed upon the stays to confine staysails at different distances. They are in place of gromcts, being more convenient as well as of a later invention. They are formed by bending a tough piece of wood into the form of a wreath, and fastened at the two ends by means of notches, thereby retaining their circular figure and elasticity, whereas the gromets, which are formed of rope, are apt to relax in warm weather, and which adhere.

HANSE towns, port-towns of Germany, of which Lnbec and Hamburgh were the chief. They were formerly all of them imperial cities, confederated for their mutual defence, and the protection of their trade.

HARBOUR, a place where ships may ride safe at anchor, chiefly used in speaking of those secured by a boom and chain, unci furnished with a mole. The bottom of the good harbour should be free from rocks and shallows : the entrance should be of sufficient extent to admit Urge ships: it should have good anchoring ground, and be easy of access; it should have room and convenience to receive the shipping of different nations: it should be furnished with a good light-house, and have at command plenty of wood and other materials for firing, besides hemp, iron, \.<\

Harbour Master, an officer appointed to inspect the moorings, and to see that the laws and regulations of the harbour are strictly attended to by the different ships.

HARDNESS, in physiology, is the resistance opposed by a body to the separation of its particles. This property depends on the force of cohesion, or on that which chemists call affinity, joined to the arrangement of the particles to their figure and other circumstances. A body, says M. Hauy, is considered more hard in proportion as it presents greater resistance to the friction of another hard body, such as a steel file ; or as it is more capable of wearing or working into such other body to which it may be applied by friction. Lapidaries judge of the hardness of fine stones, &c, from the difficulty with which they are worn down or polished.

HARE. See Lepus.

HARIOT, or Heriot, in law, a dne belonging to a lord at the death of his tenant, consisting of the best beast, either horse, ox, or cow, which he had at the time of his death; and in some manors, the best goods, piece of plate, 4tc. are called hariots.

There is both hariot-service, and hariotcustom: when a tenant holds by service to pay a hariot at his decease, which is expressly reserved in the deed of feofment, this is a hariot service; and where hariots have been customarily paid time out of mind after the death of a tenant for life, this is termed hariot custom. For hariot-service, the lord may distrain any beast belonging to the tenant that is on the land. Fur hariot-custom, the lord is to seize not distrain ; but he may seize the best beast that belonged to the tenant, though it be out of the manor, or in the king's highway, because he claims it as his proper goods by the death of his tenant. Nevertheless where a woman marries and dies, the lord shall have no hariot-custom, because a feme-covert has no goods to pay as a hariot

HARMATTAN, the name given to a singular wind which blows periodically from the interior parts of Africa towards the Atlantic ocean. It prevails in December, January, and February, and is generally accompanied with a fog or haze that conceals the son for whole day's together.

Extreme dryness is the characteristic of this wind: no dew falls during its continuance, which is sometimes for a fortnight or more. The whole vegetable creation it withered, and the grass becomes at once like hay. The natives take the opportunity which this wind gives them of clearing the land by setting fire to trees and plants in this their exhausted state. The dryness is so extreme that household furniture is damaged, and the wainscot of the rooms flies to pieces. The human body is also affected by it, so as to cause the skin to peel off, but in other respects it is deemed salutary to the constitution, by stopping the progress of infection, and curing almost all cutaneous diseases.

HARMONICA,or Armonica, isa name which Dr. Franklin has given to a musical instrument constructed with drinkingglasses. It is well known that a drinkingglass yields a sweet tone, by passing a wet finger round its brim. Mr. Pockrich, of Ireland, was the first who thought of playing tunes formed of these tones. He collected a number of glasses of different sizes, fixed them near each other on a table, and tuned them by putting into them water, more or less, as each note required. Mr. Delaval made an instrument in imitation, and from this instrument Dr. Franklin took the hint of constructing bis Armonica. The glasses for this musical instrument are blown as nearly as possible in the form of hemispheres, having each an open neck or socket in the middle. The thickness of the glass near the brim is about one tenth of an inch, increasing towards the neck, which in the largest glasses is about an inch deep, and an inch and a half wide within; but these dimensions lessen as the sue of the glasses diminish, only observing that the neck of the smallest should not be shorter than half an inch. The diameter of the largest glass is nine inches, and that of the smallest three inches: between these there are twenty-three different sizes, differing from each other a quarter of an inch in diameter. For making a single instrument there should be at least six glasses blown of each size, and out of these thirtyseven glasses (which are sufficient for three octaves with all the semitones) may be found, that will either yield the note required, or one a little sharper, and fitting so well into each other, as to taper regularly from the largest to the smallest. The glasses being chosen, and the note for which cash glass is intended being marked

« AnteriorContinuar »