this plan is to teach the blind reading, by the assistance of books, in which the letters are rendered palpable by their elevation above the surface of the paper; and by these means to instruct them, not only in the liberal arts and sciences, but likewise in the principles of mechanical operations, such as spinning, knitting, book-binding, &c. so that those who are in easy circumstances may be capable of amusing employment, and those of the lower ranks of life, and such as have no genius for literary improvement, may nevertheless become respectable, useful, and independent members of society, in the situation of common artisans. By these palpable characters, they are taught to read, to write, and to print; and they are likewise instructed, according to their several talents and stations, in geometry, algebra, geography, and every branch of natural philosophy. The institution encourages and cherishes a taste for the fine arts; it teaches the blind to read music with their fingers, as others do with their eyes; and it does this with so much success, that though they cannot at once feel the notes and perform them upon an instrument, yet they are capable of acquiring any lesson with as much exactness and rapidity, as those who enjoy all the advantages of sight.

We are happy to add, that institutions of a similar kind have been established in our own country; and to render our particular tribute of respect to the founders and supporters of the school for the indigent blind, instituted in London, 1799. The object, with a view to which this school was founded, is unquestionably one of the most im portant and interesting kind that can excite compassion, or demand encouragement. It provides instruction for the indigent blind, in a trade by which they may be able to provide, either wholly or in part, for their own subsistence; and thus, instead of being altogether a burden to the community, they will be of some service to it; and instead of being depressed and cheerless themselves, under a sense of their total dependence, and for want of regular employment, habits of industry will relieve their spirits, and produce the most beneficial effects on their state and character. The children of this institution are completely clothed, boarded, lodged, and instructed, gratis. The articles at present manufactured in the school are shoemakers'-thread, fine and coarse thread, window sash-line, and clothes-line (of a peculiar construction, and made on a machine adapted to the use

of blind persons) by the females; and window and sash-line, clothes-line, hampers, and wicker-baskets, by the males.

The success that has crowned the efforts of the friends of this institution, since its first establishment, affords sufficient evidence of the degree in which the situation and faculties of the blind are capable of improvement; and a view of it in its present prosperous state must be gratifying to persons of humane and compassionate feelings. Here they will not find the scholars sitting in listless indolence, which is commonly the case with the blind, or brooding in silence over their own defects, and their inferiority to the rest of mankind; but they will behold a number of individuals, of a class hitherto considered as doomed to a life of sorrow and discontent, and to be provided for merely in alms-houses, or by donations of charity, not less animated in their amusements, during the hours of recreation, and far more cheerfully attentive to their work in those of employment, than persons possessed of sight.

To this article we shall subjoin the following directions given by Mr. Thicknesse, for teaching the blind to write. "Let any common joiner make a flat board, about 14 inches long and 12 wide, in the middle of which let a place be sunk, deep enough, when lined with cloth, to hold only two or three sheets of fool's-cap paper, which must quite fill up the space over this must be fixed a very thin false frame, which is to cover all but the paper, and fastened on by four little pins, fixed in the lower board, and across the lower frame, just over the paper, must be a little slider, an inch and a half broad, to slip down into several recesses made in the upper frame, at a proper distance for the lines, which should be near an inch asunder; and this ruler, on which the writer is to rest his fourth and little finger, must be made full of little notches, at a quarter of an inch distant from each other; and these notches will inform the writer, by his little finger dropping from notch to notch, how to avoid running one letter into another. When he comes to the end of the line, he must move his slider down to the next groove, which may easily be so contrived with a spring to give warning that it is properly removed to the second line, and so on."

BLINDS, or BLINDES, in the art of war, a sort of defence commonly made of oziers, or branches interwoven, and laid across between two rows of stakes, about the height

of a man, and four or five feet asunder, used particularly at the heads of trenches, when they are extended in front towards the gla. cis; serving to shelter the workmen, and prevent their being overlooked by the enemy.

BLINK, of the ice, in sea language, that dazzling whiteness about the horizon which is occasioned by the reflection of light from

the fields of ice.

BLISTER, in medicine, a thin bladder containing a watery humour, whether occasioned by burns and the like accidents, or by vesicatories laid on different parts of the body for that purpose.

BLITUM, in botany, a genus of the Monandria Digynia class and order. Natural order of Holoraceæ ; Atriplices, Jussieu. Essential character: calyx trifid; petal none; seed one, with a berried calyx. There are four species, of which B.capitatum is an annual plant with leaves somewhat like those of spinach; the stalk rises about two feet and a half high in gardens; the upper part of it has flowers coming out in small heads at every joint, and is terminated by a small cluster of the same. After the flowers are past, these little heads swell to the size of wood strawberries, and when ripe have the same appearance, being very succulent and full of a purple juice, which stains the hands. It is commonly called strawberry blite, strawberry spinach, or bloody spinach; by some, berry-bearing orach. Native of Switzerland, the Grisons, Austria, the Tyrol, Spain, and Portugal.

B. virgatum seldom grows more than one foot high, with smaller leaves than the capitatum, but of the same shape. The flowers are small, and collected into little heads, shaped like those of the first, but smaller, and not s deeply coloured. A native of the South of France, Spain, Italy, and Tartary. Of the other species, the one rises more than three feet high: the other is a very low plant, and is found in Tartary and Sweden.

BLOCKS, on ship-board, is the usual name for what we call pullies at land. They are thick pieces of wood, some with three, four, or five shivers in them, through which all the running ropes run. Blocks, whether single or double, are distinguished and called by the names of the ropes they carry, and the uses they serve for.

Double blocks are used when there is occasion for much strength, because they will purchase with more ease than single blocks, though much slower,

Block and block, is a phrase signifying that two blocks meet, in haling any tackle or halliard, having such blocks belonging to them.

The blocks now used in the navy are made in Portsmouth by means of circular saws and other machinery, which have been lately erected by a most ingenious mechanician. This machinery performs the several operations from the rough timber to the perfect block, in the completest manner possible. The whole is worked by means of a steam engine; the manual labour required is simply to supply the wood as it is wanted to the several parts of the machinery, so that the commonest labourer almost may be made to act in this business with very little instruction.

Fish block is hung in a notch at the end of the davit; it serves to hale up the flooks of the anchor at the ship's brow.

Snatch block is a great block with a shiver in it, and a notch cut through one of its cheeks for the more ready receiving of any rope; as by this notch the middle part of a rope may be reeved into the block without passing it endwise. It is commonly fastened with a strap about the main-mast, close to the upper deck, and is chiefly used for the fall of the winding tackle, which is reeved into this block, and then brought to the capstan.

BLOCK house, a kind of wooden fort or battery, either mounted on rollers or on a vessel, and serving either on the water or in counterscarps and counter approaches. The name is sometimes also given to a brick or stone fort built on a bridge, or the brink of a river, serving not only for its defence but for the command of the river both above and below: such was that noted blockhouse anciently on the bridge of Dresden, since demolished on enlarging the bridge.

BLOCKADE, in the art of war, the blocking up a place by posting troops at all the avenues leading to it, to keep supplies of men and provisions from getting into it; and by these means proposing to starve it out without making any regular attacks.

To raise a blockade is to force the troops that keep the place blocked up from their posts.

BLOOD is a well-known fluid, which eirculates in the veins and arteries of the more perfect animals. It is of a red colour, has a considerable degree of consistency, and an unctuous feel, as if it contained a quantity of soap. Its taste is slightly saline, and it has a peculiar smell.

The specific gravity of human blood is, at a medium, 1.05. Mr. Fourcroy found the specific gravity of bullock's blood, at the temperature of 60°, to be 1.056. The blood does not uniformly retain the same consistence in the same animal, and its consistence in different animals is very various, It is easy to see that its specific gravity must be equally various. When blood, after being drawn from an animal, is allowed to remain for some time at rest, it very soon coagulates into a solid mass, of the consistence of curdled milk. This mass gradually separates into two parts, one, of which is fluid, and is called serum; the other, the coagulum, has been called cruor, because it alone retains the red colour which distinguishes blood. This separation is very similar to the separation of curdled milk into curds and whey. The proportion between the cruor and serum of the blood. varies much in different animals, and even in the same animal in different circumstances. The most common proportion is about one part of cruor to three parts of serum. 1. The serum is of a light greenish yellow colour: it has the taste, smell, and feel of the blood, but its consistence is not so great. It converts syrup of violets to a green, and therefore contains an alkali. On examination, Roulle found that it owes this property to a portion of soda. When heat ed to the temperature of 156o, the serum coagulates. It coagulates also when boiling water is mixed with it, but if serum be mixed with six parts of cold water, it does not coagulate by heat. When coagulated, it has a greyish white colour, and is not unlike the boiled white of an egg. If the coagulum be cut into small pieces, a muddy fluid may be squeezed from it, which has been termed the serosity. After the separation of this fluid, if the residuum be carefully washed in boiling water and examined, it will be found to possess all the properties of coagulated albumen. The serum, there fore, contains a considerable proportion of albumen. Hence its coagulation by heat, and the other phenomena which albumen usually exhibits. If serum be diluted with six times its weight of water, and then boiled to coagulate the albumen, the liquid which remains after the separation of the -coagulum, if it be gently evaporated till it becomes concentrated, and then be allowed to cool, assumes the form of a jelly. Consequently it contains gelatine. If the coagulated serum be heated in a silver vessel, the surface of the silver becomes black,

heing converted into a sulphuret. Hence it is evident, that it contains sulphur; and Proust has ascertained that it is combined with ammonia in the state of a hydrosulphuret. If serum be mixed with twice its weight of water, and, after coagulation by heat, the albumen be separated by filtration, and the liquid be slowly evaporated till it is considerably concentrated, a number of crystals are deposited when the liquid is left standing in a cool place. These crystals consist of carbonate of soda, muriate of soda, besides phosphate of soda and phosphate of lime. The soda exists in the blood in a caustic state, and seems to be combined with the gelatine and albumen. The carbonic acid combines with it during evaporation. Thus it appears that the serum of the blood contains albumen, gelatine, hydrosulphuret of ammonia, soda, muriate of soda, phosphate of soda, and phosphate of lime. These component parts account for the coagulation occasioned in the serum by acids and alcohol, and the precipitation produced by tannin, acetate of lead, and other metallic salts. The cruor, or clot, as it is sometimes called, is of a red colour, and possesses considerable consistence. Its mean specific gravity is about 1.245. If this cruor be washed carefully, by letting a small jet of water fall upon it, till the water runs off colourless, it is partly dissolved, and partly remains upon the searce. Thus it is separated into two portions: namely, 1. A white, solid elastic substance, which has all the properties of fibrin; 2. The portion held in solution by the water, which consists of the colouring matter, not, however, in a state of purity, for it is impossible to separate the cruor completely from the serum. We are indebted to Bucquet for the first precise set of experiments on this last watery solution. It is of a red colour. Bucquet proved that it contained albumen and iron. Menghini had ascertained, that if blood be evaporated to dryness by a gentle heat, a quantity of iron may be separated from it by the magnet. The quantity which he obtained was considerable; according to him, the blood of a healthy man contains above two ounces of it. Now, as neither the serum nor the fibrin extracted from the cruor contains iron, it follows of course, that the water holding the colouring matter in solution must contain the whole of that metal. This watery solution gives a green colour to syrup of violets. When exposed to the air, it gradually deposits flakes, which have the

properties of albumen. When heated, a brown-coloured scum gathers on its surface. If it be evaporated to dryness, and then mixed with alcohol, a portion is dissolved, and the alcoholic solution yields by evapo ration a residuum, which lathers like soap in water, and tinges vegetable blues green; the acids occasion a precipitate from its solution. This substance is a compound of albumen and soda. Thus we see that the watery solution contains albumen, iron, and soda. When new-drawn blood is stirred briskly round with a stick or the hand, the whole of the fibrin collects together upon the stick, and in this manner may be separated altogether from the rest of the blood. The red globules in this case remain behind in the serum. It is in this manner that the blood is prepared for the different purposes to which it is put; as clarifying sugar, making puddings, &c. After the fibrin is thus separated, the blood no longer coagulates when allowed to remain at rest, but a spongy flaky matter separates from it, and swims on the surface.

BLUE, otherwise called azure, is one of the primitive colours of the rays of light. BLUE, painters, is made different according to the different kinds of painting.

In limning, fresco, and miniature, they use indifferently ultramarine, blue ashes, and smalt: these are their natural blues, excepting the last, which is partly natural and partly artificial.

In oil and miniature they also use indigo prepared; as also a fictitious ultramarine.

Enamellers and painters upon glass have blues proper to themselves, each preparing them after their own manner.

BLUING of iron, a method of beautifying that metal sometimes practised; as for mourning buckles, swords, or the like. The manner is thus: take a piece of grindstone and whetstone, and rub hard on the work to take off the black scurf from it; then heat it in the fire, and as it grows hot the colour changes by degrees, coming first to a light, then to a dark gold colour, and lastly to a blue. Sometimes they grind also indigo and sallad oil together, and rub the mixture on the work with a woollen rag while it is heating, leaving it to cool of itself. Among sculptors we also find mention of bluing a figure of bronze, by which is meant the heating of it to prepare it for the application of gold leaf, because of the bluish cast it acquires in the operation.

BLUENESS, that quality which denomipates a body blue, depending on such a size

and texture of the parts that compose the surface of a body, as dispose them to reflect the blue or azure rays of light, and those only, to the eye.

With respect to the blueness of the sky, M. de la Hire, after Leonardo da Vinci, observes, that any black body, viewed through a thin white one, gives the sensation of blue; and this he assigns as the reason of the blueness of the sky, the immense depth of which, being wholly devoid of light, is viewed through the air illuminated and whitened by the sun. For the same reason, he adds, it is, that soot mixed with white makes a blue; for white bodies, being always a little transparent, and mixing them. selves with a black behind, give the perception of blue. From the same principle he accounts for the blueness of the veins on the surface of the skin, though the blood they are filled with be a deep red; for red, he observes, unless viewed in a clear, strong light, appears a dark brown, bordering on black: being then in a kind of obscurity in the veins, it must have the effect of a black; and this, viewed through the membrane of the vein and the white skin, will produce the perception of blueness.

In the same way did many of the early writers account for the phenomenon of a blue sky; but, in the explanation of this phenomenon, Sir Isaac Newton observes, that all the vapours, when they begin to condense and coalesce into natural particles, become first of such a bigness as to reflect the azure rays, before they can constitute clouds of any other colour. This, therefore, being the first colour which they begin to reflect, must be that of the finest and most transparent skies, in which the vapours are not arrived to a grossness suffi cient to reflect other colours.

M. Bouguer, without having recourse to the vapours diffused through the atmosphere, in order to account for the reflection of the blue-making rays, ascribes it to the constitution of the air itself, whereby these fainter-coloured rays are incapable of making their way through any considerable tract of it; and he accounts for those blue shadows, which were first observed by M. Buffon in the year 1742, by the aërial colour of the atmosphere, which enlightens these shadows, and in which the blue rays prevail; whilst the red rays are not reflected so soon, but pass on to the remoter regions of the atmosphere.

The Abbé Mazeas, in a Memoir of the Society in Berlin, for the year 1752, ac

counts for the phenomenon of blue shadows, by the diminution of light; having observed, that of two shadows which were cast upon a white wall, from an opaque body illuminated by the moon, and by a candle at the same time, that which was enlightened by the candle was reddish, and that which was enlightened by the moon was blue. However, the true cause of this appearance seems to be that assigned by M. Bouguer, which agrees with the solution given of it about the same time by Mr. Melville. But, instead of attributing the different colours of the clouds, as Sir Isaac Newton does, to the different size of those globules into which the vapours are condensed; Mr.Melville supposes, that the clouds only reflect and transmit the sun's light; and that, according to their different altitudes, they may assume all the variety of colours at sun-rising and setting, by barely reflecting the sun's incident light, as they receive it through a shorter or longer tract of air: and the change produced in the sun's rays by the quantity of air through which they pass, from white to yellow, from yellow to orange, and lastly to red, may be understood agreeably to this hypothesis, by applying to the atmosphere what Sir Isaac Newton says concerning the colour of transparent liquors in general, and that of the infusion of lignum nephriticum in particular.

BLUSHING, a suffusion or redness of the cheeks, excited by a sense of shame on account of a consciousness of some failing or imperfection.

Blushing is supposed to be produced from a kind of consent or sympathy between the several parts of the body, occasioned by the same nerve being extended to them all. Thus the fifth pair of nerves being branched from the brain to the eye, ear, muscles of the lips, cheeks and palate, tongue and nose; a thing seen or heard that is shameful affects the cheeks with blushes, driving the blood into their minute vessels at the same time that it affects the eye and ear. Mr, Derham further observes, upon this subject, that a savory thing seen or smelt affects the glands and parts of the mouth; if a thing heard be pleasing, it affects the muscles of the face with laughter; if melancholy, it exerts itself on the glands of the eyes, and occasions weeping, &c. To the same cause is, by others, the pleasure of kissing ascribed.

B MOLLARRE, or MOLLE, one of the notes of the scale of music, usually called soft or flat, in opposition to b quadro.

BOA, in natural history, a genus of serpents, of which the generic character is, plates on the belly and under the tail, witha rattle. Gmelin mentions ten species only, but Dr. Shaw and others enumerate as many as eighteen. B. contortrix is found in Carolina, and has about 150 plates on the belly, and 40 on the tail; it is broad with a convex back; colour cinereous, with lateral round spots; has a poisonous bag, but no fangs; tail from one third to a half the length of the whole body: it is very slow in its motions. B. constrictor, is very remarkable for its vast size, some of the principal species which are met with in India, Africa, and South America, have been seen between 30 and 40 feet long, and possessed of so much strength as to be able to kill cattle by twisting around them and crushing them to death by pressure, after which they devour them, eating till they are almost unable to move; in that state they may be easily shot. Dr. Shaw observes that these gigantic serpents are become less common, in proportion to the increased population of the parts where they are found; they are, however, still to be seen, and will approach the abodes in the vicinity of their residence. This species is beautifully variegated with rhombic spots; belly whitish; is of vast strength and size, measuring 30 and 36 feet long. With respect to age, sex, and climate, it is subject to considerable variations. It is supposed that an individual of this species once diffused terror and dismay in a whole Roman army, a fact alluded to by Livy in one of the books that have not come to us, but which is quoted by Valerius Maximus, in words to the following effect: "Since we are on the subject of uncommon phenomena, we may here mention the serpent so eloquently recorded by Livy, who says, that near the river Bagrada in Africa, a snake was seen of so enormous a magnitude as to prevent the army of Attilius Regulus from the use of the river; and after snatching up several soldiers with its enormous mouth and devouring them, and killing several more by striking and squeezing them with the spires of its tail, was at length destroyed by assailing it with all the force of military engines and showers of stones, after it had withstood the attack of their spears and darts: that it was regarded by

than even Carthage itself; and that the