The oxymuriatic acid has also been used from its bleaching power in the manufacture of paper; either the linen rags from which the paper is to be made being blanched by it, or, what has been regarded as preferable, the pulp into which they are reduced being submitted to its action. This method, though once extensively practised in this country, has been relinquished by many of our paper-manufacturers,as it has been found, that in paper prepared with it, in the course of a few years the ink is altered, and its blackness even so much impaired, as to afford some reason for the suspicion that in time it will altogether fade; nor is this confined to writing ink, but has been observed even in printing ink. The effect is no doubt to be ascribed to a slight impregnation of the oxymuriatic acid; and this indeed can often be rendered perceptible by its odour, by breathing on paper which has been bleached in this manner. It might no doubt be removed by very careful washing of the pulp; but we have been informed by some intelligent paper manufacturers, that the additional labour which would be requisite for this would upon the whole render the method more expensive than the old one. The process of bleaching by steam with an alkali at a high temperature, might probably be advantageously employed. A branch of the manufacture, however, in which the acid necessarily must be used, is that of discharging the colours from coloured rags, or to remove the ink from waste written paper. Even printed paper has been whitened by its agency, combined with that of an alkali, to remove the oily matter, and made to afford at least a coarser kind of paper. Chaptal applied it to the purpose of restoring the colour of old books or prints, the paper being whitened by a very dilute acid, which did not act sensibly on the printing ink, Wax, reduced to thin plates, has been bleached by the oxymuriatic acid. The process succeeds best when the acid is used in the state of gas. Berthollet has announced a peculiar effect obtained from the action of oxymuriatic acid, that of giving the appearance of cotton to hemp or flax. The process consists in immersing the flax, prepared by boiling, and by an alkaline solution in oxymuriatic acid of a certain strength, for some time, and alternating this immersion repeatedly with the action of an alkaline ley. BLECHNUM, in botany, a genus of the Cryptogamia Filices, or Ferns. There are six species, all of them natives of warm or hot countries, excepting B.virginicum, which will bear the open air of England. They are increased by parting the roots. BENDE. See ZINC. BLENNIUS, blenny, in natural history, a genus of fishes of the order Jugulares. The generic characters are, head sloping; body lengthened, sub-compressed, lubricous; gill membrane six-rayed; ventral fins two, three, or four-rayed, unarmed; anal fin distinct. There are two divisions; viz. A. head crested; B. head not crested; and according to Gmelin there are 18 species, though Dr. Shaw enumerates more. B. galerita, or crested blenny, inhabits the European ocean, is four or five inches long; its body is brown and spotted; the skin at the corner of the upper jaw loose, projecting; dorsal fin extending from the head almost to the tail; ventral fin small; vent under the ends of the pectoral fin. This fish is frequently found about the rocky coasts of Great Britain. B. ocellaris has above the eyes a single ray, and on the first dorsal fin a large black ocellate spot. It inhabits the Mediterranean Sea; is eight inches long; the body is without scales, dirty green, with olive streaks, rarely pale blue; the flesh is eatable, but in no great estimation. Although Linnæus and others have described this fish as having two dorsal fins, Block considers it as having in reality but one, the sinking in of the middle part being in some specimens much deeper than in others, seems to be the cause of this difference of opinion. B. saliens is a very small species, observed about the coasts of some of the southern islands, and particularly those of New Britain. It seems to be of a gregarious nature, and is seen swimming by hundreds, and flying as it were over the surface of the water, occasionally springing among the rocks. It is naturally formed for celerity in its movements, the pectoral fins being very large in proportion to the body. They are nearly of a circular form when expanded, and when contracted reach almost as far as the vent on each side. B. superciliosus has a small head, with large eyes, and silvery irides, and immediately over each eye is situated a small palmated crest, or appendage, divided into three segments. The body is covered with very small scales, and is of a yellow or gilded tinge, and marked with numerous and irregular spots of dusky red. The dorsal fin commences at the back part of the head, and is continued almost to the tail; but near its commence ment suddenly sinks, so as almost to give the appearance of a smaller anterior dorsal fin, separate from the longer one: the pectoral fins are of moderate size; the ventral ones didactyle, and rather long: the vent is situated in the middle of the abdomen, from which part the anal fin commences, and reaches as far as the tail. This species is found native in the Indian seas, grows to the length of about twelve inches, and is viviparous. There is, however, another species, denominated B, viviparus, which, like that just noticed, is distinguished by a particularity that takes place in but very few fishes, except those of the cartilaginous tribe; being viviparous, the ova hatching internally, and the young acquiring their perfect form before the time of birth. Not less than two, or even three hundred of these have been sometimes observed in a single fish. It might be imagined that so great a number, confined in so small a space, might injure each other by the briskness of their motions; but this is prevented by the curious disposition of fibres and cellules among which they are distributed, as well as by the fluid with which they are surrounded. When advanced far in its pregnancy, it is scarcely possible to touch the abdomen without causing the immediate exclusion of some of the young, which are instantly capable of swimming with great alertness. The B. viviparus is littoral fish, and is found about the coasts of the Mediterranean, and the Baltic and Northern Seas, and sometimes it enters the mouths of rivers. It feeds on the smaller fishes, &c. It is taken by the line and net; but is not estimated as food, as its bones acquire a greenish colour by boiling. See Plate II. Pisces: fig. 2. BLIGHT, in agriculture, a general name for various distempers incident to corn and fruit trees. It affects them variously, the whole plant sometimes perishing by it, and sometimes only the leaves and blossoms, which will be scorched and shrivelled up, the rest remaining green and flourishing. Some have supposed that blights are produced by easterly winds, which bring vast quantities of insects' eggs along with them from distant places. These being lodged upon the surface of the leaves and flowers of fruit trees, cause them to shrivel up and perish. Mr. Knight, however, observes that blights are produced by a variety of causes, by insects, by an excess of heat or cold, of drought or moisture; for these necessarily derange and destroy the delicate organiza tion of the blossoms. The term blight is very frequently used by the gardener and farmer without any definite idea being annexed to it. If the leaves of their trees be eaten by the cater, pillar, or contracted by the aphis; if the blossoms fall from the ravages of insects, or without any apparent cause, the trees are equally blighted; and if an east wind happen to have blown, the insects, or at least their eggs, whatever be their size, are supposed to have been brought by it. The true cause of blight seems to be, continued dry easterly winds for several days together, without the intervention of showers or any morning dew, by which the perspiration in the tender blossom is stopped; and if it so happen that there is a long continuance of the same weather, it equally affects the tender leaves, whereby their colour is changed and they wither and decay. The best remedy, perhaps, is gently to wash and sprinkle over the tree, &c. from time to time, with common water; and if the young shoots seem to be much infected let them be washed with a woollen cloth, so as to clear them, if possible, from this glutinous matter, that their respiration and perspiration may not be obstructed. This operation ought to be performed early in the day, that the moisture may be exhaled before the cold of the night comes on; nor should it be done when the sun shines very hot. Another cause of blights in the spring, is said to be sharp hoary frosts, which are often succeeded by hot sun-shine in the day. time. This is the most sudden and certain destroyer of fruit that is known. The chief remedy to be depended upon in this case is, that of protecting the fruit trees during the night-time with nets. This mode, where regularly and correctly performed, has been found highly beneficial. What is termed the blight is frequently, however, no more than a debility or distemper in trees. Mr. Forsyth observes, that "this is the case when trees against the same wall and enjoying the same advan tages in every respect, differ greatly in their health and vigour, the weak ones appearing to be continually blighted, while the others remain in a flourishing condition. This very great difference, in such circumstances, can be attributed only to the different constitutions of the trees proceeding from want of proper nourishment, or from some bad qualities in the soil; some distemper in the stock, buds, or scions; or from some mismanagement in the pruning, &c. all of which room. are productive of distempers in trees, of which they are, with difficulty, cured. If the fault be in the soil it must," he says, “be dug out and fresh mould put in its place; or, the trees must be taken up, and others, better adapted to the soil, planted in their It will be found absolutely necessary always to endeavour to suit the particular sorts of fruit to the nature of the soil; for it is in vain to expect all sorts of fruit to be good in the same soil. If the weakness of the tree proceed from an in-bred distemper it will be adviseable to remove it at once, and after renewing the earth to plant another in its place." But if the weakness is brought on by ill management in the pruning, which is frequently the case, he would advise more attention to the method of pruning and training. Besides this, "there is another sort of blight that sometimes happens pretty late in the spring, as in April or May, which is very destructive to fruit trees in orchards and open plantations, and against which we know of no effectual remedy. This is what is called a fire-blast, which, in a few hours, hath not only destroyed the fruit and leaves, but often parts of trees; and sometimes entire trees have been killed by it." As this generally happens in close plantations where the vapours from the earth and the perspiration from the trees are pent in for want of a free circulation of air to disperse them; it points out to us the only way yet known of guarding against this enemy to fruits; namely, to make choice of a clear healthy situation for kit chen-gardens, orchards, &c. and to plant the trees at such a distance as to give free admission to the air, that it may dispel those vapours before they are formed into such volumes as to occasion these blasts." But blasts may also be occasioned by the reflection of the sun's rays from hollow clouds, which sometimes act as burning mirrors, and occasion excessive heat. See APHIS. BLINDNESS, a total privation of sight, arising from an obstruction of the functions of the organs of sight, or from an entire deprivation of them. This defect may arise from a variety of causes, existing either in the organ of sight, or in the circumstances necessary to produce vision. Blindness will be complete, when the light is wholly excluded; or partial, when it is admitted into the eye so imperfectly as to convey only a confused perception of visible objects. Blindness may again be distinguished into periodical or permanent, transient or perpetual, natu ral or accidental, &c.; but these distinctions do not serve to communicate any idea of the causes of blindness. We find various recompenses for blindness, or substitutes for the use of the eyes, in the wonderful sagacity of many blind persons, recited by Zahnius, in his "Oculus Artificialis," and others. In some, the de. fect has been supplied by a most excellent gift of remembering what they had seen; in others, by a delicate nose, or the sense of smelling; in others, by an exquisite touch, or a sense of feeling, which they have had in such perfection, that, as it has been said of some, they learned to hear with their eyes; as it may be said of these, that they taught themselves to see with their hands. Some have been enabled to perform all sorts of curious and subtle works in the nicest and most dexterous manner. Aldrovandus speaks of a sculptor who became blind at twenty years of age, and yet, ten years after, made a perfect marble statue of Cosmo II. de Medicis; and another of clay like Urban VIII. Bartholin tells us of a blind sculptor in Denmark, who distinguished perfectly well, by mere touch, not only all kinds of wood, but all the colours; and F. Grimaldi gives an instance of the like kind; besides the blind organist, living in Paris, who is said to have done the same. The most extraordinary of all is a blind guide, who, according to the report of good writers, used to conduct the merchants through the sands and desests of Arabia. James Bernouilli contrived a method of teaching blind persons to write. An instance, no less extraordinary, is mentioned by Dr. Bew, in the "Transac tions of the Manchester Society." It is that of a person, whose name is John Metcalf, a native of the neighbourhood of Manchester, who became blind at so early an age as to be altogether unconscious of light and its various effects. His employment in the younger period of his life was that of a waggoner, and occasionally as a guide in intricate roads during the night, or when the common tracks were covered with snow. Afterwards he became a projector and surveyor of highways in difficult and mountainous parts; and, in this capacity, with the assistance merely of a long staff, he traverses the roads, ascends precipices, explores valleys, and investigates their several extents, forms, and situations, so as to answer his purpose in the best manner. His plans are designed, and his estimates form. red, with such ability and accuracy, that he has been employed in altering most of the roads over the Peak in Derbyshire, particularly those in the vicinity of Buxton, and in constructing a new one between Wilmslow and Congleton, so as to form a communication between the great London road, without being obliged to pass over the mountain. of Didymus in Alexandria, who, "though blind from his infancy, and therefore ignorant of the letters, appeared so great a miracle to the world, as not only to learn logic, but geometry also to perfection, which seems (he adds) the most of any thing to require the help of sight." Professor Saunderson, who was deprived of his sight by the small pox, when he was only twelve months old, seems to have acquired most of his ideas by the sense of feeling; and though he could not distinguish colours by that sense, which, after repeated trials, he said was pretending to impossibilities, yet he was able, with the greatest exactness, to discriminate the minutest difference of rough and smooth in a surface, or the least defect of polish. In a set of Roman medals, he could distinguish the genuine from the false, though they had been counterfeited in such a manner, as to deceive a connoisseur, who judged of them by the eye. His sense of feeling was so acute, that he could perceive the least variation in the state of the air; and, it is Although blind persons have occasion, in a variety of respects, to deplore their infelicity, their misery is in a considerable degree alleviated by advantages peculiar to themselves. They are capable of a more fixed and steady attention to the objects of their mental contemplation, than those who are distracted by the view of a variety of external scenes. Their want of sight naturally leads them to avail themselves of their other organs of corporeal sensation, and with this view to cultivate and improve them as much as possible. Accordingly they derive relief and assistance from the quickness of their hearing, the acuteness of their smell, and the sensibility of their touch, which persons who see are apt to dis-said, that in a garden where observations regard. Many contrivances have also been devised by the ingenious for supplying the want of sight, and for facilitating those analytical or mechanical operations, which would otherwise perplex the most vigorous mind and the most retentive memory. By means of these they have become eminent proficients in various departments of science. Indeed there are few sciences in which, with or without mechanical helps, the blind have not distinguished themselves. The case of Professor Saunderson at Cambridge is well known. His attainments and performances in the languages, and also as a learner and teacher in the abstract mathematics, in philosophy, and in music, have been truly astonishing; and the account of them appears to be almost incredible, if it were not amply attested and confirmed by many other instances of a similar kind, both in ancient and modern times. Cicero mentions it as a fact scarcely credible, with respect to his master in philosophy, Diodotus, that "he exercised himself in it with greater assiduity after he became blind; and which he thought next to impossible to be performed without sight; that he professed geometry, and described his diagrams so accurately to his scholars, as to enable them to draw every line in its proper direction." were made on the sun, he took notice of every cloud that interrupted the observation, almost as justly as those who could see it. He could tell when any thing was held near his face, or when he passed by a tree at no great distance, provided the air was calm, and there was little or no wind: this he did by the different pulse of air upon his face. He possessed a sensibility of hearing to such a degree, that he could distinguish even the fifth part of a note; and, by the quickness of this sense, he not only discriminated persons with whom he had once conversed so long as to fix in his memory the sound of their voice, but he could judge of the size of a room into which he was introduced, and of his distance from the wall; and if he had ever walked over a pavement in courts, piazzas, &c. which reflected a sound, and was afterwards conducted thither again, he could exactly tell in what part of the walk he was placed, merely by the note which it sounded. Sculpture and painting are arts which, one would imagine, are of very difficult and almost impracticable attainment to blind persons; and yet instances occur, which shew that they are not excluded from the pleasing, creative, and extensive regions of fancy. De Piles mentions a blind sculptor, who thus took the likeness of the Duke de Brac Jerom relates a more remarkable instance ciano in a dark cellar, and made a marble statue of King Charles I. with great just- mined with such a degree of accuracy, as ness and elegance. However unaccountable it may appear to the abstract philosophers, yet nothing is more certain in fact, than that a blind man may, by the inspiration of the Muses, or rather by the efforts of a cultivated genius, exhibit in poetry the most natural images and animated descriptions even of visible objects, without deservedly incurring the charge of plagiarism. We need not recur to Homer and Milton for attestations to this fact; they had probably been long acquainted with the visible world before they had lost their sight, and their descriptions might be animated with all the rapture and enthusiasm which originally fired their bosoms, when the grand and delightful objects delineated by them were immediately beheld. We are furnished with instances in which a similar energy and transport of description, at least in a very considerable degree, have been exhibited by those on whose minds visible objects were never impressed, or have been entirely obliterated. Dr. Blacklock affords a surprising instance of this kind, who, though he had lost his sight before he was six months old, not only made himself master of various languages, Greek, Latin, Italian, French; but acquired the reputation of an excellent poet, whose performances abound with appropriate images and animated descriptions. Another instance, which deserves being recorded, is that of Dr. Henry Moyes, in our own country, who, though blind from his infancy, by the ardour and assiduity of his application, and by the energy of na tive genius, not only made incredible advances in mechanical operations, in music, and in the languages; but acquired an extensive acquaintance with geometry, optics, algebra, astronomy, chemistry, and all other branches of natural philosophy. From the account of Dr. Moyes, who occasionally read lectures on philosophical chemistry at Manchester, delivered to the Manchester society by Dr. Bew, it appears, that mechanical exercises were the favourite employment of his infant years: and that at a very early age he was so well acquainted with the use of edge tools, as to be able to construct little wind-mills, and even a loom. By the sound, and the different voices of the persons that were present, he was directed in his judgment of the dimensions of the room in which they were assembled; and in this respect he deter seldom to be mistaken. His memory was singularly retentive; so that he was capable of recognizing a person on his first speaking, though he had not been in company with him for two years. He determined with surprising exactness the stature of those with whom he conversed, by the direction of their voices; and he made tolerable conjectures concerning their dispositions, by the manner in which they conducted their conversation. His eyes, though he never recollected his having seen, were not totally insensible to intense light: but the rays refracted through a prism, when sufficiently vivid, produced distinguishable effects upon them. The red produced a disagreeable sensation, which he compared to the touch of a saw. As the colours declined in violence, the harshness lessened, until the green afforded a sensation that was highly pleasing to him, and which he described as conveying an idea similar to that which he gained by running his head over smooth polished surfaces. Such surfaces, meandering streams, and gentle declivities, were the figures by which he expressed his ideas of beauty; rugged rocks, irregular points, and boisterous elements, furnished him with expressions for terror and disgust. He excelled in the charms of conversation; was happy in his allusions to visual objects; and discoursed on the nature, composition, and beauty of colours, with pertinence and precision. This instance, and some others which have occurred, seem to furnish a presumption, that the feeling or touch of blind persons may be so improved as to enable them to perceive that texture and disposition of coloured surfaces by which some rays of light are reflected and others absorbed, and in this manner to distinguish colours. It redounds very much to the honour of modern times, that the public attention has been directed to the improvement of the condition of blind persons; and that institutions have been formed in different countries for providing them with suitable employment, tending not only to alleviate their calamity, but to render them useful. The first regular and systematic plan for this purpose was proposed by M. Hally in an" Essay on the Education of the Blind," printed at Paris in the year 1786, under the patronage of the Academy of Sciences. An English translation of this essay is annexed to "Dr. Blacklock's Poems," printed at Edinburgh in 1793, 4to. The object of |