heart-shaped leaves, and clusters of purplish flowers, which are succeeded by capsules of a heart-shaped form, covered with stiffish bristles, and opening into two valves which contain, attached to their middle, a number of seeds covered with a soft, sticky, vermilion-coloured rind. It is the

tion, and he pursued it experimentally with great vigour | adding any fresh experiments, he answered and refuted all and commensurate success. the objections which had been urged against him.

The chemical subject which seems first peculiarly to have excited his attention was connected with his profession as a physician, and is thus detailed by Dr. Robison in the preface to Dr. Black's 'Lectures on the Elements of Chemistry :'It was the good fortune of chemical science that at this very time the opinions of professors were divided concerning the manner in which certain lithontriptic medicines, and particularly lime-water, acted in alleviating the excruciating pains of the stone and gravel. The students usually partake of such differences of opinion, and are thereby animated to more serious study, and science gains by their emulation. This was a subject quite suited to the taste of young Mr. Black, one of Dr. Cullen's most zealous and intelligent chemical scholars. It was indeed a most interesting subject, both to the chemist and the physician. All the medicines which were then in vogue, as solvents of the calculous concretion, resembled more or less the lapis infernalis, and the common ley of the soap-boilers, two substances so terribly acrimonious, that in a very short time they will reduce the firmest and most solid parts of the animal body to a mere pulp. Therefore, while they were powerful lithontriptics they were hazardous medicines, if in unskilful hands. All of them seem to derive their efficacy from quick-lime, and this derives its power from the fire. Its wonderful property of becoming intensely hot, and even sometimes ignited, when moderately wetted with water, had long engaged the attention of chemists. It was therefore very natural for them to ascribe its power to igneous matter imbibed from the fire, retained in the lime, and communicated by it to alkalies and other substances, which it renders so powerfully acrid. Hence undoubtedly arose the denomination of causticity, given to the quality so induced. I see that Mr. Black had entertained the opinion, that caustic alkalies acquired igneous matter from quicklime. In one memorandum he hints at some way of catching this matter as it escapes from lime, while it becomes mild by exposure to the air, but on the opposite blank page is written-Nothing escapes, the cup rises considerably by absorbing air.' A few pages after this, he compares the loss of weight sustained by an ounce of chalk when calcined, with its loss when dissolved by spirit of salt. Immediately after a medical case is mentioned which I know to have occurred in November, 1752. From this it would appear that he had before this time suspected the real nature of these substances. He had then prosecuted his inquiry with vigour : the experiments with magnesia are soon mentioned.

In 1756, Dr. Cullen having removed to Edinburgh, Dr. Black was appointed professor of anatomy and lecturer on chemistry in the University of Glasgow, where he continued till 1766, when he was appointed to the chemical chair in Edinburgh. Between the years 1759 and 1763 he matured the speculations on heat which had for a long period occasionally occupied his thoughts. Boerhaave has recorded an observation made by Fahrenheit, that water would become considerably colder than melting snow, without freezing, and would freeze in a moment if disturbed, and in the act of freezing emitted many degrees of heat. This notice seems to have supplied Dr. Black with some vague notion that the heat received by ice during its conversion into water was not lost, but was contained in the water. The experiments by which Dr. Black demonstrated the existence of what he termed latent heat in bodies, are extremely simple and easy of execution. He remarks (Lectures,' vol. i. p. 119) that melting ice receives heat very fast, but the only effect of this beat is to change it into water, which is not in the least sensibly warmer than the ice was before.' 'A great quantity therefore of the heat, or of the matter of heat, which enters into the melting ice, produces no other effect but to give it fluidity, without augmenting its sensible heat; it appears to be absorbed and concealed within the water, so as not to be discoverable by the application of a thermometer.'

In order to understand,' he continues, this absorption of heat into melting ice, and concealment of it in the water, more distinctly, I made the following experiments:—The plan of the first was, to take a mass of ice, and an equal quantity of water, in separate vessels of the same size and shape, and as nearly as possible of the same heat, to suspend them in the air of a warm room, and by observing with a thermometer the celerity with which the water is heated or receives heat, to learn the celerity with which it enters the ice; and the time necessary for melting the ice being also attended to, to form an estimate from these two data of the quantity of heat which enters into ice during its liquefaction. He exposed in the same room a given quantity of water frozen into ice, and an equal quantity of water at 33°, and as the result of the experiment he states, that it was necessary that the glass with the ice receive heat from the air of the room during twenty-one half-hours, in order to melt the ice into water, and to heat that water to 40° of Fahrenheit. During all this time it was receiving the heat, or the matter of heat, with the same celerity (very nearly) with which the water-glass received it during the single half-hour in the first part of the experiment. For, as the water received it with a celerity which was diminishing gradually during that half-hour, in consequence of the diminution of difference between its degrees of heat and that of the air; so the glass with the ice also received heat with a diminishing celerity, which corresponded exactly with that of the water-glass, only that the progression of this diminution was much more slow, and corresponded to the whole time which the water surrounding the ice required to become warmed to 40° of Fahrenheit. The whole quantity of heat therefore received by the ice-glass during the twenty-one half-hours was twenty-one times the quantity received by the water-glass during the single half-hour. It was therefore a quantity of heat which, had it been added to the liquid water, would have made it warmer by (40-33) × 21, or 7 × 21, or 147°. No part of this heat however appeared in the ice-water, except 8°; the remaining 139°, or 140° had been absorbed by the melting ice, and were concealed in the water into which it was changed.'

These laid open the whole mystery, as appears by one other memorandum :- When I precipitate lime by a common alkali there is no effervescence: the air quits the alkali for the lime, but it is not lime any longer, but c. c. c. It now effervesces, which good lime will not. He had now discovered that the terrible acrimony of these powerful substances is their native property, and not any igneous property derived from the lime, and by the lime from the fire. He had discovered that a cubic inch of marble consisted of about half its weight of pure lime, and as much air as would fill a vessel holding six wine gallons, and that it was rendered tasteless and mild by this addition, in the same manner as oil of vitriol is rendered tasteless and mild in the form of alabaster, by its combination with calcareous earth.' Having thus most satisfactorily proved to what the causticity of lime and the alkalies was owing, he made it the subject of his inaugural thesis, which he entitled De Acido a cibis orto, et de Magnesiâ.' This occurred in 1754, when the degree of doctor of medicine was conferred upon him by the University of Edinburgh. In the following year he He then mentions that another obvious method of melting published his Experiments on Magnesia, Quicklime, and ice occurred to him, in which it would be still more easy to other Alkaline Substances.' In this the views which had perceive the absorption and concealment of heat, by the been but little more than indicated in his thesis were de-action of warm water. For the details of these very simple tailed at greater length, and the whole subject more fully developed.

Dr. Black's experiments and opinions respecting causticity gave rise to considerable discussion; and they were especially attacked by Dr. Meyer of Osnaburg, who had published a considerable volume on quicklime, in which he professed to explain all the phenomena by the action of an acidum pingue, formed in the lime during calcination, and consisting of igneous matter in a certain inexplicable combination with other substances. Though this work was replete with injudicious experiments and incorrect reasoning, it gave Dr. Black considerable uneasiness; and without

yet most satisfactory experiments, we must content ourselves with referring to Dr. Black's 'Lectures,' vol. i. p. 123. In page 157 of the same volume he proves that in the case of boiling the heat absorbed does not warm surrounding bodies, but converts the water into vapour, and he adds, in both cases, considered as the cause of warmth, we do not perceive its presence: it is concealed, or latent, and I gave it the name of latent heat.' It was indeed by Dr. Black's doctrine respecting the nature of steam that Mr. Watt was led to his great improvements in the steam-engine, a sufficient proof, if indeed proof were required, of the immense importance of his discoveries.

The Philosophical Transactions' for 1775 contain a short paper by Dr. Black, giving an account of some experiments, showing that recently-boiled water begins to freeze more speedily than water that has not been boiled, and he explains the cause of its so doing. The only other paper written by Dr. Black was published in the second volume of the Transactions of the Royal Society of Edinburgh. It is an analysis of the Geyser and Rikum springs in Iceland, in which he found a considerable quantity of silica.

attendants to come near to them. At the time of their death they would be very strong and vigorous, but if they escaped it, then they were to the contrary. It spared no complexion or constitution, and the choleric it chiefly molested. That which is most to be admired is, that no women were taken away by it, or poor people, or such that administered physic, or any that came to visit. But as the physicians were ignorant of the causes, so also of the cures of this disease.' Holinshed says that no child died of this infection. Dr. Black was never married. He died on the 26th of No- It seems more than probable that the distemper which vember, 1799, in the seventy-first year of his age. Dr. Ro- arose on this occasion, was a fever originating in the poibison (Preface to Lectures, p. lxii.) says, As to the manner sonous condition of the adjoining gaol, where the prisoners in which Dr. Black acquitted himself in his public character had been long, close, and nastily kept. Wood mentions a of a professor, I need only say that none contributed more similar event at Cambridge, at the assizes held in the castle largely to establish, and support and increase the high cha- there in the time of Lent, 13 Henry VIII., A.D. 1521, where racter which the University of Edinburgh has acquired. His the justices, all the gentlemen, bailiffs, and most who retalent for communicating knowledge was not less eminent sorted thither, took such an infection, that many of them than for observation and inference from what he saw. He died, and all almost that were present sickened, and narsoon became one of the principal ornaments of the Univer- rowly escaped with their lives. sity; and his lectures were attended by an audience which continued increasing from year to year, for more than thirty years. It could not be otherwise. His personal appearance and manners were those of a gentleman, and peculiarly pleasing. His voice in lecturing was low, but fine; and his articulation so distinct, that he was perfectly well heard by an audience consisting of several hundreds. His discourse was so plain and perspicuous, his illustration by experiment so apposite, that his sentiments on any subject never could be mistaken even by the most illiterate; and his instructions were so clear of all hypothesis or conjecture, that the hearer rested on his conclusions with a confidence scarcely exceeded in matters of his own experience.'

BLACK-ASSIZE, the name given to a fatal assize held in 1577 in the old town-hall of Oxford, situated at that time in the yard of the castle. Holinshed and Stow make particular mention of it in their Chronicles, but the best account of it is in Anthony à Wood's History and Antiquities of the University, published by Gutch, 4to. Oxford, 1796, vol. ii. p. 188, when noticing the trial of one Rowland Jencks, a book-binder, for sedition. He says-The assizes therefore being come, which began the 4th of July, and continued two days after in the court-house at the castle-yard, the said Jencks was arraigned and condemned in the presence of a great number of people to lose his ears. Judgment being passed, and the prisoner taken away, there arose such an infectious damp or breath among the people, that many there present, to the apprehensions of most men, were then smothered, and others so deeply infected that they lived not many hours after. The persons that then died,' he adds, ' and were infected by the said damp, when sentence was passed, were Sir Robert Bell, baron of the Exchequer; Sir Nicholas Barham, sergeant-at-law; Sir Robert D'Oyley, the high-sheriff; Hart, his under-sheriff; Sir William Babyngton, Robert D'Oyley, Wenman, Danvers, Fetiplace, and Harcourt, justices of the peace; Kerle, Greenwood, Nash, and Forster, gentlemen; besides most of the jury, with many others that died within a day or two after. Above 600 sickened in one night, as a physician of Oxford (Georg. Edrycus in Hypomnematibus suis in aliquot libros Pauli Egineta, edit. Lond. 1588, lib. 2) attested; and the day after, the infectious air being carried into the next villages, there sickened 100 more. The 15th, 16th, and 17th days of July sickened also above 300 persons, and within twelve days' space died 100 scholars, besides many citizens. The number of persons that died in five weeks' space, namely from the 6th of July to the 12th of August (for no longer did this violent infection continue), were 300 in Oxford, and 200 and odd in other places: so that the whole number that died in that time were 510 persons, of whom many bled till they expired. Some, Wood says, 'left their beds, occasioned by the rage of their disease and pain, and would beat their keepers or nurses, and drive them from their presence. Others ran about the streets and lanes in a state of phrenzy, and some even leaped headlong into deep waters. The physicians fled, not to avoid trouble,' he says, but to save themselves and theirs.' The heads of houses and doctors almost all fled; and there was not a single college or hall, but had some taken away by this infection. The parties,' Wood says, that were taken away by this disease were troubled with a most vehement pain of the head and stomach, vexed with the phrenzy, deprived of their understanding, memory, sight, hearing, &c. The disease also increasing, they could neither eat nor sleep, nor would suffer any

Father Sanders (in his book De Schismate Angl. lib. iii.), noticing the black-assize of Oxford, called it ingens miraculum,' and ascribed it as a just judgment on the cruelty of the judge for sentencing the bookbinder to lose his ears. A contemporary account of the black-assize is given in a letter from Sergeant Fleetwood, recorder of London, to Lord Burleigh, dated 30th July, 1577, printed in Ellis's Original Letters Illustrative of English History (second series, vol. iii. p. 54); and another contemporary account, in Latin, from the Register of Merton College, was communicated to the Royal Society by professor Ward in 1758, and is printed in the Philosophical Transactions for that year, vol. 1. part ii. p. 699.

(See also Holinshed's Chron. edit. 1587, vol. ii. p. 1270; Stow's Annals, edit. 1631, p. 681; and Pointer's Antiquities and Curiosities of Oxford, 8vo. Lond. 1749, p. 171.)

BLACKBIRDS (zoology), the English name for birds of the first tribe of the genus Turdus, Linn., belonging to the fifth family (Les Turdusinées) of Cuvier's second order (Les Passereaux), according to Lesson's arrangement.

But the term Blackbird is more exclusively applied in England to that well-known natiye songster, Merula vulgaris of Ray, Turdus Merula of Linnæus, the Schwarzdrossel and Schwarze Amsel of the Germans, Merle of the French, Merla and Merlo of the Italians, and KórTupos, or kórovpoc (cóttyphus or cóssyphus), of the antient Greeks.

The Blackbird is too well known to require a description; but a word or two on the subject of its habits may not be misplaced. There are not wanting those who praise the song-thrush at the expense of the blackbird, alleging that, though the former commits depredation in our fruit gardens in summer, it makes amends by its destruction of the shellsnails (Helices aspersa et nemoralis), whereas the blackbird is a most notorious fruit-eater, without any such redeeming quality. That the thrush does this service is most true; but it is not less true that the blackbird is particularly fond of the shell-snails, which it devours in the same way with the thrush. In truth, small slugs and shell-snails, to use the expression of a garden labourer, form the chief of its living,' while the thrush is equally fond of fruit in the season; but the plumage of the thrush is in its favour, and it is often pecking away at the fruit without being seen. When disturbed it glides away without noise; but the blackbird's sharp cry of alarm as it escapes generally strikes the ear, if its black coat and yellow bill have not arrested the eye. Thus much in justice to the blackbirds; for we know of instances where a war of extermination has been waged against them, while the thrushes have been held sacred.

Early in the spring the blackbird begins to build its nest. A thick-set hedge-row, an insulated close bush, a low ivied tree, are all favourite places. Moss, small sticks, rootfibres, are the materials, with an internal coat of mud-plaster, over which is a lining of fine dry grass. Four or five eggs of a bluish-green, variegated with darker markings, are here deposited. Aristotle (book v. c. 13.) observes, that it lays twice, and Buffon says that the first deposit ranges from five to six eggs, but the second only from four to five. The early season at which it begins to lay is often so cold as to destroy the first brood; moreover, the leafless state of the hedge or bush at that period makes the nest an easy prey to the school-boy.

The blackbird is in general shy, but there are exceptions to the remark,

In the spring of 1829 we saw a hen blackbird sitting on | Willughby (book 2, p. 195.) there is the following pasher nest in the camellia-house belonging to Messrs. Lod- sage. In a bird that I described at Rome, the edges of diges at Hackney. It was built in a camellia close to the the prime feathers of the wings, as also of the covert feawalk; so close, that a passer-by might have touched the thers of the head and wings were cinereous. The ring also bird; but there she sat, and, undisturbed by the crowds who was not white but ash-coloured. I suppose this was either were attracted to the view of the noble and luxuriant collec- a young bird or a hen. Montagu speaks of it as breeding tion in full bloom, there she safely hatched and brought up in some parts of Wales, on Dartmoor in Devonshire, and her young. near the Land's End in Cornwall, as well as in the north In the spring of 1834 a pair of blackbirds built their nest of England and Scotland. The same author says, that he in a faggot-pile close to the door of a kitchen-garden in the has received it from the mountainous parts of Ireland. We parish of Sunbury, Middlesex, where the garden-labourers have seen it on Dartmoor in the breeding season; and in the were passing all day long wheeling manure into the garden, spring of 1829 several were seen and somes hot near Bristol. &c. The nest was built among some dead thorns there piled In the catalogue of Dorset birds, Ring-ouzels are said to up, so low that the passer-by could look into it, and was very appear in Portland (where they are called Michaelmas much exposed: but the parents, notwithstanding the cu- blackbirds) when on their autumnal and spring flights. riosity of spectators, brought up their nestlings. This was Slaney says, Mr. White gives an account of his discovery a late brood; and as many early nests had been taken in of these birds in Hampshire, in October; and we bave seen the neighbouring hedge-rows, it is not impossible that the them near the Isle of Thanet, probably on their return birds, disappointed of their first brood, might have been southward after rearing their young. They are said to driven to choose a spot nearer the house for security. breed on Dartmoor, and in the Peak of Derbyshire; and we have observed them among the heath on the Welch mountains in July. Sir W. Jardine speaks of their depredations when they descend to the gardens from the mountains previous to their migration to winter quarters, and says that they are known to the country people under the title of mountain blackbirds.'

Albinos sometimes occur among these birds.* Several instances are recorded: the following from 'Loudon's Magazine (No. 43, p. 596) is one of the latest. In 1829 a blackbird's nest, containing four or five young ones, was found at Rougham, near Bury St. Edmunds, Suffolk. One of the young ones differed in colour materially from the rest. Its eyes were red, its bill was yellow (which is not usual in very young blackbirds). The nest was not taken till the young were fully fledged. On attempting to capture them, two or three made their escape; the white one was safely caught.***The red-eyed bird afterwards became nearly or wholly white, and it still retains this colour. In the British Museum there is a female of a dusky white or cream-colour, with Yorkshire for its locality.

H. Bruce Campbell, Esq., lately presented a male entirely white to the Zoological Society, in whose garden at the Regent's Park it is now (1835) living. It was found in June, 1832, at Belsthorpe, Nottinghamshire. There were two other young ones in the nest, the plumage of which, as well as that of the parents, was of the ordinary colour. Bechstein, in his interesting little book on cage-birds, says, 'the white variety is very well-known; there is, besides, the streaked, the black with a white head, and the pearl gray. The same author gives the following account of the musical properties of the blackbird in confinement. Its voice is so strong and clear, that in a city it may be heard from one end of a long street to the other. Its memory is so good, that it retains without mixing them several airs at once, and it will even repeat little sentences. It is a great favourite with the lovers of a plaintive, clear, and musical song, and may in these respects be preferred to the bullfinch, whose voice is softer, more flute-like, but also more melancholy. The price of these two birds, if well taught, is about the same.'

The Ring-blackbird, Merula torquata, Ring-ouzel or Amzel of Ray, Merle au collier of the French, Merulo Alpestro of the Italians, Ringamsel, Ringel Amsel and Ringdrossel of the Germans, Turdus torquatus, Linn., Merle à plastron blanc of Buffon, is a periodical visitant, and, contrary to the habits of its congeners, such as the Field-fare and Red wing, arrives in spring, seeking the mountainous and stony down-districts of Great Britain, where it breeds.

The nest and eggs very much resemble those of the blackbird in size and colour, and are generally placed in some bush or grass-tuft among the heath, and about the rocks, on a shelf or in a cleft. When its young are hatched it has no longer the shy character which, at other seasons, renders it so difficult to be approached; for it then becomes apparently bold, drawing the attention of the observer by loud cries and extravagant gestures, in order to lead him away from its nest. On the approach of autumn it retires southwards, and about the end of October leaves us for warmer climates. In Sweden, France, and Germany it is common. Bechstein says, though it traverses the whole of Europe, it builds only in the north. Temminck speaks of it as rare in Holland. We have searched in vain for it in Prince Bonaparte's Specchio Comparativo, but in Ray's

• Aristotle (book ix. chap. 19.) mentions the white variety xλsuxes, observing that in size it is equal to the black, and that its voice is nearly the same, το δε μέγεθος ἶσος ἐκείνῳ, καὶ ἡ φωνη παραπλησια ἐκείνῳ.” He adds, that it is found in Arcadia, v Kuλλnyn Tns Agxadias, and no where else. Varro, de re Rustica (book iii.), says that white blackbirds were shown in public at Rome, with parrots, &c

Buffon observes, that they appeared in small flocks of twelve or fifteen, about Montbard in Burgundy in the beginning of October, seldom staying more than two or three weeks, and that the least frost made them disappear: but at the same time he states, that Klein declares that the birds had been brought alive to him in the middle of winter, and that though they very rarely inhabit the plains of temperate Europe, M. Salerne asserts that their nests have been found in Sologne and in the forest of Orleans. Pennant, who gives them the name Muyalchen y graig, referring to Camden, among his synonyms, says Ringouzels inhabit the Highland hills, the north of England, and the mountains in Wales. They are also found to breed in Dartmoor, in Devonshire, in banks on the sides of streams. I have seen them in the same situation in Wales, very clamorous when disturbed. He further observes, The place of their retreat is not known; those that breed in Wales and Scotland never quitting these countries.'

Latham, in a note to the last edition of Pennant says, 'This species is met with in the warmer and the colder regions, as well in Africa as Asia; but does not inhabit either Russia or Siberia, though it is seen in Persia about the Caspian Sea.' Buffon also gives it a wide geographical distribution

The parish of Blackburn is very large, extending nearly fourteen miles in length, and ten in breadth. It contains fifteen townships and eight chapelries, viz., Blackburn, Clayton-le-dale, Cuerdale, Lower Darwen, Dinkley, Ecclesnill, Little Harwood, Livesley, Mellor, Osbaldeston, Pleas- But, for a long period, the chief article manufactured ington, Ramsgrave, Rishton, Wilpshire, and Wilton, town-here was calicoes, for which the Blackburn weavers were ships; along with Balderston, Billington, Over Darwen, celebrated. This branch of trade is now transferred to Great Harwood, Salisbury, Samlesbury, Tockholes, and the power-looms, and the remnant of hand-loom weavers Walton-le dale, Chapelries. This district is only a small are chiefly employed, at the present time, in making lowpart of the hundred of Blackburn, whose boundaries are priced muslins. A considerable section of the working marked by the hundred of Amounderness on the north-community are engaged in the mills, which are increasing east, by the Darwent and the hundred of Leyland on the west, and by the hundred of Salford on the south. It comprises four whole parishes, Blackburn, Chipping, Ribchester, and Whalley, and parts of Bury and Metton, altogether containing eighty townships. This hundred contributes 302 men to the county militia; and the inhabitants pay nine parts in every hundred to the county rate.