Imágenes de páginas
PDF

young, it is tamed with great ease, and will accompany the ducks to the ponds, and the poultry in general to their roosts. The general food of these birds, in their natural state, consists of shell-lish; they will, with astonishing ease, force the limPct from the rock, notwitlistanding its tehacious hold, and it is said that on perFeiving the slightest opening of its shells by an oyster, they insert their bills in it with admirable dexterity, and tear the te*''' from his mansion. See Aves, Plate Wil fig. 6. H.EMATOXYLUM, in botany, a ge" of the Decandria Monogynia class and order. Natural order of Lomenta* Leguminosae, Jussieu. Essential ‘haracter; calyx five-parted, petals five; logume lanceolate; valves boat-shaped. There is but one species, viz. H. campe*inum, logwood, blood-wood, or com. Peche-wood. This tree grows naturally in the bay of Campeche, at Honduras, old many parts of the Spanish West-Indies, where it frequently rises to four-andtwenty feet in height. HEMORRHolids, or Piles. See MEDICINE. HitRUCA, in natural history, a genus of the Vermes Intestina class and order. Body cylindrical, the fore-part two-necked, and surrounded with a single row of prickles, without any proboscis. Only one occles is mentioned by Gmelin, viz. the H. muris, which inhabits the intestines of the moose, and is distinguished from the genus Echinorhynchus, by being destitute of the retractile proboscis. HAIL, on natural history, a meteor generally defined frozen rain, but differing from ": in that the hailstones are not form. *d of single pieces of ice, but of many lit**pherules agglutinated together; neither are these spherules aii of the same **ei, some of them being hard and solid, like perfectice; others soft, and mostly like snow hardened by a se*** frost. Hail-stone has a kind of core of this soft matter; but more frequently the core is solid and hard, while the outside is formed of a softer matter. Hailo assume various figures, being some**, round, at other "times pyramidal, ofenated, angular, thin, and flat, and ometimes stellated with six radii, like the small £osstals of snow. Natural histo*fornish us with various accounts of to: showers of hail, in which the . *... were of extraordinary magni. o o: these we mention one or two, (i. o ohappened in England. that Jr. Halley, and others also, relate, at in Cheshire, Lancashire, &c. April

29th, 1697, a thick, black cloud, comiug from Carnarvonshire, disposed the vapours to congeal in such a manner, that, for about the breadth of two miles, which was the limit of the cloud, in its progress for the space of sixty miles, it did inconceivable damage; not only killing all sorts of fowls and other small animals, but splitting trees, knocking down horses and men, and even ploughing up the earth; so that the hail-stones buried themselves under ground an inch or an inch and a half deep. The hail-stones, many of which weighed five ounces, and some half a pound, and being five or six inches about, were of various figures; some rosind, others half round; some smooth, others embossed and crenated; the icy substance of them was very transparent and hard, but there was a snowy kernel in the middle of them. “In Hertfordshire, May 4, the same }. after a severe storm of thunder and ightning, a shower of hail succeeded, which far exceeded the former; some persons were killed by it, and their bodies beaten all black and blue; vast oaks were split, and fields of rye cut down as with a scythe. The stones ineasured from ten to thirteen or fourteen inches about. Their figures were various, some oval, others picked, and some flat.” Phil. Trans. Number 229. See MEtronology. HAILING, in naval language, the salutation or accosting a ship at a distance, which is usually performed with a speaking-trumpet : the first exclamation is, “hoa, the ship, ahoy,” to which she replies, “holloa,” then follow the requisite questions and replies. HAIR, small filaments issuing out of the pores of the skins of animals, and serving most of them as a tegument or covering. In lieu of hair, the nakedness of some animals is covered with feathers, wool, scales, &c. Hair is found on all parts of the human body, except the soles of the feet and the palms of the hands; but it grows longest on the head, chin, breast, in the armpits, &c. It is known that every hair does properly and truly live, and receive nutriment to fill and distend it like the other parts; which they argue hence, that the roots do not turn grey in aged persons sooner than the extremities, but the whole changes colour at once, and the like is observed in boys, &c. which shows, that there is a direct communication, and that all the parts are affected alike. It may be observed, however that, in propriety, the life and growth a hairs is of a different kind from that of the rest of the body, and is not immediately derived therefrom, or reciprocated therewith. It is rather of the nature of vegetalion. They grow as plants do out of the earth; or, as some plants shoot from the parts of others, from which, though they draw their nourishment, yet each has, as it were, its several life, and a distinct economy. They derive their food from some juices in the body, but not from the nutritious juices; whence they may live though d. body be starved. The hairs ordinarily appear round or cylindrical; but the microscope also discovers triangular or square ones, which diversity of figure arises from that of the pores, to which the hairs always accommodate themselves. Their length depends on the quantity of the proper humour to feed them, and their colour on the quality of that humour: whence, at different stages of life, the colour usually differs. Their extremities split into two or three branches, especially when kept dry, or suffered to grow too long; so that what appears only a single hair to the naked cye, seems a brush to the microscope.— The hair of a mouse, viewed by Mr. Derham with a microscope, seemed to be one single transparent tube, with a pith made up of fibrous substances, running in dark lines, in some hairs transversely, in others spirally. The darker medullary parts or lines, he observes, were no other than small fibres convolved round, and lying closer together than in the other parts of the hair; they run from the bottom to the top of the hair, and, he imagines, may serve to make a gentle evacuation of some humour out of the body; hence, the hair of hairy animals, this author sug. gests, may not only serve as a fence against cold, &c. but as an organ of insensible perspiration. Hair makes a very considerable article in commerce, especially since the mode of perukes has obtained. The hair of the growth of the northern countries, as England, &c. is valued much beyond that of the more southern ones, as Italy, Spain, the south parts of France, &c. The merit of good hair consists in its being well fed, and neither too coarse nor too slender; the bigness rendering it less susceptible of the artificial curl, and disposing it rather to frizzle, and the smallness making its curl of too short duration. Its length should be about twenty-five inches; the more it falls short of this, the less value it bears. The scarceness of grey and white hair has put the dealers in that commodity upel, the methods of reducing other colours to these. This is done by spreading the hair to bleach on the grass like linen, after

first washing it out in a bleaching water: this ley, with the force of the sun and air, brings the hair to so perfect a whiteness, that the most experienced person may be deceived therein, there being scarce any way of detecting the artifice, but by boil. ing and drying it, which leaves the hair of the colour of a dead walnut-tree leaf. . like wool, may be dyed of any coour.

Hair, which does not curl or buckle naturally, is brought to it by art, by first boiling, and then baking it, in the follow: ing manner: after having picked and sorted the hair, and disposed it in parcels according to lengths, they roll, them up, and tie them tight down upon little cylindrical instruments, either of wood or earthen ware, a quarter of an inch thick, and hollowed a little in the middle, called pipes; in which state they are put in a pot over the fire, there to boil for about two hours. When taken out, they let them dry; and when dried, they spread them on a sheet of brown paper, cover them with another, and thus send them to the pastry-cook, who making a crust or coffin around them, of common paste, sets them in an oven till the crust is about three-fourths baked. The end by which a hair grows to the head is called the head of the hair; and the other, with which they begin to give the buckle, the point. Formerly, the peruke-makers made no difference between the ends, but curled and wove them by either indifferently; but this made them unable to give a fine buckle, hair woven by the point never taking a right curl.

Hair is also used in various other arts and manufactures: in particular the hair of beavers, hares, conies, &c. is the principal matter whereof hats are made. Spread on the ground, and left to putrefy on corn-lands, hair, as all other animal substances, viz. horns, hoofs, blood, &c. proves good manure.

This, like every part of the animal system, has been ão, analysed, and has been found to contain a large portion of gelatine, which may be separated from it by boiling. It then becomes brittle, the gelatine being the principal cause of its suppleness and toughness. From some . by Mr. Hatchett, it is interred, 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 288 Gases . . . . 271 Coal . . . . . 324 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 Dow N, 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

resent themselves under various forms ;

in the leguminous plants they are generally cylindric; in the mallow tribe, ter. minated in a point; in agrimony, shaped like a fish-hook; in nettle, awl shaped and jointed; and in some compound flowers, with hollow or funnel-shaped florets, they are terminated in two crooked Points.

HAIR's breadth, a measure o, 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 under jaw longest. It grows to two feet or more in length, but

is the slenierest of all the gadi. See GADUs. HALBARD, or HALhent, 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 two-edged 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 adjustmg the files of a battalion. HALE, in the sea language, signifies ull ; as to hale up, is to pull up ; to hale in or out, is to pull in or out. To overhale a rope, is to hale it too stiff, or to hale it the contrary way.

HALES, (Stephes,) 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 in 1702. He afterwards proceeded M. A. and entered into holy orders. During his resi: dence 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 Stukely, afterwards M. D. and an eminent antiquary. A turn of novel and ingenious experiments, and of mechanical inventions, early characterised 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 o 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 mem. ber of the Royal Society, o in the following year he read before that body an account of some experiments concerning the effect of the sun’s heat 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-Statical 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, cusus paucissimos habemus aemulos quitoties 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 nutricious juice through their capillary tubes, and considers the lateral motion of this juice from trunk to branches, and vice versa. It dis.

roves any proper circulation of this fluid, É. 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 Haemastatics; or an account of some Hydraulic and Hydrostatical experiments made on the Blood and Blood-vessels of Animals; also, an Account of some Experiments on Stones in the Kidneys and Bladder, &c.” In this he discussed some fundamental points relative to o , 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 calcu

lus relates to its chemical composition, and to the means of dissolving it; of which, suggested by him, 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. Stephen’s celebrated medicines, in 1749. 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 1733, 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, anonymously, “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’ inventions 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 gaol-fever 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 back-heaver, 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 1753, 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 at Teddington, was not unknown to many persons of rank, whom he visited, and received at his house with all the simplicity of his modest and unaf. fected 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 habi. tual 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 eighty-fourth year, and was buried under the tower of the church, which he had rebuilt at his own expense. 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 Doolecandria Monogynia class and order. Natural order of Bicornes. Guajacanae, Jussieu. 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 eight-pence. HALF moon, in fortification, an outwork composed of two faces, forming a saliant 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 ; spire lateral, and almost concealed. There are nineteen species, of which H. tuberculata is the most common ; it inhabits southern Europe, and gradually disappears towards the north. The shell is subovate, the outside transversely grooved, rugged, and tuberculate. The inside is like mother of pearl. When living, it adheres to rocks. According to Pennant, this was the sea-ear of Aristotle. HALL, in architecture, an avenue or room at the entrance of a building. HALL is also a public building or court of justice, as Westminster-hall, Guildhall, 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. Scrophulariae, Jussieu. Essential character : calyx trifid ; corolla quadrifid; filaments longer than the corolla; berry inferior, twocelled. 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 METEOrtology.

HALORAGIS, in botany, a genus of the Octandria Tetragynia class and order. Natural order of Calycanthema. Onagrae, Jussieu. Essential character; calyx fourcleft, superior; petals four; drupe dry, inclosing a four-celled nut. There are two species, viz. H. prostrata 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; . nut two-hormed, two-celled. There is only one species, viz. H. virginica, witch hazel.

« AnteriorContinuar »