must take the contrary direction. But this way of explaining, by a change in the force of the earth, supposes that the changing cause is acting in opposition to some other force. We do not know of any such. The force, whatever it is, seems simply to produce its own effect, in deranging the needle from the direction of terrestrial magnetism. If Epinus's theory of magnetic action be admitted, viz. that a bar of steel has magnetism induced on it by propelling the quiescent and mutually repelling particles of magnetic fluid to one end, or attracting them to the other, we may suppose that the sun acts on the earth as a magnet acts on a piece of soft iron, and in the morning propels the fluid in the north-west parts. The needle directs itself to this constipated fluid, and therefore it points to the eastward of the magnetic north in the afternoon. And (to abide by the same theory) this induced magnetism will be somewhat greater when the earth is warmer; and therefore the diurnal variation will be greatest in summer. This change of position of the constipated fluid must be supposed to bear a very small ratio to the whole fluid, which is naturally supposed to be constipated in one pole of the great magnet, in order to give it magnetism. Thus we shall have the diurnal variation a very small quantity. This is departing, however, from the principle of Mr. Canton's explanation; and indeed we cannot see how the weakening the general force of the terrestrial magnet should make any change in the needle in respect to its direction; nor does it appear probable that the change of temperature produced by the sun will penetrato deep enough to produce any sensible effect on the magnetism. And, if this be the cause, we think that the derangements of the needle should vary as the thermometer varies, which is not true. The other method of explaining is much better, if Epinus's theory of magnetic attraction and repulsion be just; and we may suppose that it is only the secondary magnetism (i. e. that of the magnetisable minerals) that is sensibly affected by the heat; this will account very well for the greater mobility of the fluid in summer than in winter. A great objection to either of these explanations is the prodigious diversity of the diurnal variations in different places. This is so very great that we can hardly ascribe the diurnal variations to any change in the magnetism of the primitive terrestrial magnet, and must rather look for its cause in local circumstances. This conclusion becomes more probable, when we learn that the deviation from the meridian and the deviation from the horizontal line are not affected at the same time. Van Swinden ascribes them solely to changes produced on the needles themselves. If their magnetism be greatly deranged by the sun's position, it may throw the magnetic centre away from the centre of the needle's motion, and thus may produce a very small change of position. But, if this be the cause, we should expect differences in different needles. Van Swinden says that there are such, and that they are very great; but as he has not specified them, we cannot draw any conclusion.

The aurora borealis is observed (in Europe)

to disturb the needle exceedingly, sometimes drawing it several degrees from its position. It is always observed to increase its deviation from the meridian, that is, an aurora borealis makes the needle point more westerly. This disturbance sometimes amounts to six or seven degrees, and is generally observed to be greatest when the aurora borealis is most remarkable. This is a very curious phenomenon, and we have not been able to find any connexion between this meteor and the position of a magnetic needle. It is to be observed, that a needle of copper or wood, or any substance besides iron, is not affected. We long thought it an electric phenomena, and that the needle was affected as any other body balanced in the same manner would be; but a copper needle would then be affected. Indeed it may still be doubted whether the aurora borealis be an electric phenomenon. They are very frequent and remarkable in Sweden; and yet Bergman says that he never observed any electric symptoms about them, though in the mean time the magnetic needle was greatly affected. We see the needle frequently disturbed both from its general annual position, and from the change made on it by the diurnal variation. This is probably the effect of aurora boreales which are invisible, either on account of thick weather or day-light. Van Swinden says he seldom or never failed to observe aurora boreales immediately after any anomalous motion of the needle; and concluded that there had been one at the time, though he could not see it. Since no needle but a magnetic one is affected by the aurora borealis, we may conclude that there is some natural connexion between this meteor and magnetism. This should farther incite us to observe the circumstance formerly mentioned, viz. that the south end of the dipping needle points to that part of the heavens where the rays of the aurora appear to converge. We wish that this were diligently observed in places which have very different variation and dip of the mariner's needle. For the diurnal and this irregular variation, consult the Dissertations of Celsius and of Hiorter, in the Memoirs of Stockholm; Wargentin, Philosophical Transactions, vol. 48. Braun (Comment Petropol. Novi, T. V. VII. IX.); Graham and Canton. See also MAGNETISM.

VARIATION OF CURVATURE, in geometry, is used for that inequality or change which takes place in the curvature of all curves except the circle, by which their curvature is more or less in different parts of them; and this variation constitutes the quality of the curvature of any line. VARICOUS, adj. Į

VAR'IX, N. s.

a dilatation of the vein.

cous,

Latin varix, varicosus. Diseased with dilatation:

There are instances of one vein only being variwhich may be destroyed by tying it above and below the dilatation. Sharpe. In ulcers of the legs, accompanied with varices or dilatations of the veins, the varix can only be assisted by the bandage.

Id.

VARICOUS, or VARICOSE. See SURGERY. VARIETY, orVARIETAS, in botany, is a change in some less essential part or quality; as color, size, pubescence, or age. Externally; by the

1722.

VARILLAS (Antony), historian, born at Gueret in 1624. He wrote a History of France, Anecdotes of Florence, &c., and died in 1696. VARINAS, a province of the Caraccas, bounded on the north by the provinces of Maracaibo and Venezuela, east by the plains of Caraccas and the Orinoco, west by Merida and New Granada, and south by Juan de los Llanos, or Casanare. This province was formed in the year 1787, by separating the southern districts of Venezuela and Maracaibo, when it was also constituted a distinct government. The chief products are tobacco, cattle, sugar, coffee, cotton, indigo, and all the fruits of the torrid zone. Varinas is intersected by numerous large and navigable rivers, which occasionally inundate and fertilise its plains. Of these the Apure, the Portuguesa, the Guanarito, the Bocono, Guanapalo, the Arauca, the Capanaparo, the Sinaruco, and the Meta are the most noted.

VARINAS, the capital of the above province, ' is situated about 300 miles south-east of Caraccas. It is a neat little place.

VARINI, a people of Germany.-Tacit. de Ger. 40.

VARIOLE, the small-pox. See MEDICINE,

Index.

VARIOLA, in medicine (Lat. varius, because it disfigures the skin), the small-pox. A genus of disease in the class pyrexia, and order exanthemata, of Cullen. It is distinguishable by synocha, eruption of red pimples on the third day, which on the eighth day contain pus, and afterwards by drying fall off in crusts. This very contagious disease is supposed to have been introduced into Europe from Arabia, where there arises a fever, that is succeeded by a number of little inflammations in the skin, which proceed to suppuration, of which the matter formed is capable of communicating the disorder. It makes its attack on people of all ages, but the young of both sexes are most liable to it; and, though it will prevail at all seasons, it is most prevalent in the spring and

summer.

The red small-pox is distinguished into the distinct and confluent, implying that in the former the eruptions are perfectly separate from each other, and that in the latter they run much into one another. Both species are produced

either by breathing air impregnated with the effluvia arising from the bodies of those who labor under the disease, or by the introduction of a small quantity of the variolous matter into the habit by inoculation; and it is probable that the difference of the small-pox is not owing to any difference in the contagion, but depends on the state of the person to whom it is applied, or on certain circumstances concurring with the application of it.

Four different states or stages are observed in the small pox: first the febrile; second the eruptive; third the maturative; and fourth that of the declination or scabbing.

When the disease has arisen naturally, and is of the distinct kind, the eruption is commonly preceded by a redness in the eyes, soreness in the throat, pains in the head, back, and loins, weariness and faintness, alternate fits of chilliness and heat, thirst, nausea, inclination to vomit, and a quick pulse. In some instances these symptoms prevail in a high degree, and in others they are very moderate and trifling. In very young children, startings and convulsions are apt to take place a short time previous to the appearance of the eruption, always giving great alarm to those not conversant with the frequency of the occurrence.

About the third or fourth day from the first seizure, the eruption shows itself in little red spots on the face, neck, and breast, and these continue to increase in number and size for three or four longer, at the end of which time they are to be observed dispersed over several parts of the body. If the pustules are not numerous the febrile symptoms will generally go off on the appearance of the eruption, or then will become very moderate.

It sometimes happens that a number of little spots of an erysipelatous nature are interspersed amongst the pustules; but these generally go in again, as soon as the suppuration commences, which is usually about the fifth or sixth day, at which period, a small vesicle containing an almost colorless fluid may be observed upon the top of each pimple. Should the pustules be perfectly distinct and separate from each other, the suppuration will probably be completed about the eighth or ninth day, and they will then be filled with a thick yellow matter; but, should they run much into each other, it will not be completed till some days later.

When the pustules are very thick and numerous on the face, it is apt about this time to become much swelled, and the eye-lids to be closed up, previous to which there usually arises a hoarseness and difficulty of swallowing, accompanied with a considerable discharge of viscid saliva. About the eleventh day the swelling of the face usually subsides, together with the affection of the fauces, and is succeeded by the same in the hands and feet, after which the pustules break, and discharge their contents; and then, becoming dry, they fall in crusts, leaving the skin which they covered of a brown-red color, which appearance continues for many days. In those cases where the pustules are large, and are late in becoming dry and falling off, they are very apt to leave pits behind them; but where they

are small, suppurate quickly, and are few in number, they neither leave any marks behind them, nor do they occasion much affection of the system.

In the confluent small-pox, the fever which precedes the eruption is much more violent than in the distinct, being attended usually with great anxiety, heat, thirst, nausea, vomiting, and a frequent and contracted pulse, and often with coma or delirium. In infants, convulsive fits are apt to occur, which either prove fatal before any eruption appears, or they usher in a malignant species of the disease. The eruption usually makes its appearance about the third day, being frequently preceded or attended with a rosy efflorescence, similar to what takes place in the measles; but the fever, although it suffers some slight remission on the coming out of the eruption, does not go off as in the distinct kind; on the contrary, it becomes increased after the fifth or sixth day, and continues considerable throughout the remainder of the disease.

As the eruption advances, the face, being thickly beset with pustules, becomes very much swelled, the eye-lids are closed up, so as to deprive the patient of sight, and a gentle salivation ensues, which, towards the eleventh day, is so viscid as to be spit up with great difficulty. In children a diarrhoea usually attends this stage of the disease instead of a salivation, which is to be met with only in adults. The vesicles on the top of the pimples are to be perceived sooner in the confluent small-pox than in the distinct; but they never rise to an eminence, being usually flatted in; neither do they arrive to proper suppuration, as the fluid contained in them, instead of becoming yellow, turns to a brown color. About the tenth or eleventh day, the swelling of the face usually subsides, and then the hands and feet begin to puff up and swell, and about the same time the vesicles break, and pour out a liquor that forms into brown or black crusts, which, upon falling off, leave deep pits behind them, that continue for life; and, where the pustules have run much into each other, they then disfigure and scar the face very considerably.

Sometimes it happens that a putrescency of the fluids takes place at an early period of the disease, and shows itself in livid spots interspersed among the pustules, and by a discharge of blood by urine, stool, and from various parts of the body.

In the confluent small-pox, the fever, which perhaps had suffered some slight remission from the time the eruption made its appearance to that of maturation, is often renewed with considerable violence at this last-mentioned period, which is what is called the secondary fever, and this is the most dangerous stage of the disease. It has been observed, even amongst the vulgar, that the small-pox is apt to appear immediately before or after the prevalence of the measles. Another curious observation has been made relating to the symptoms of these complaints, namely, that if, while a patient labors under the small-pox, he is seized with the measles, the course of the former is retarded till the eruption of the measles is finished. The measles appear for instance on the second day of the eruption of

small-pox; the progress of this ceases till the measles terminate by desquamation, and then it goes on in the usual way. Several cases are, however, recorded in the Medical and Physical Journal, as likewise in the third volume of the Medical Commentaries, in which a concurrence of the small-pox and measles took place without the progress of the former being retarded. The distinct small-pox is not attended with danger, except when it attacks pregnant women, or approaches nearly in its nature to that of the confluent; but this last is always accompanied with considerable risk, the degree of which is ever in proportion to the violence and permanence of the fever, the number of pustules on the face, and the disposition to putrescency which prevails. When there is a great tendency this way, the disease usually proves fatal between the eighth and eleventh day, but in some cases death is protracted till the fourteenth or sixteenth. The confluent small-pox, although it may not prove immediately mortal, is very apt to induce various morbid affections.

Both kinds of small-pox leave behind them a predisposition to inflammatory complaints, particularly to ophthalmia and visceral inflammations, but more especially of the thorax; and they not unfrequently excite scrofula into action which might otherwise have lain dormant in the system.

The treatment of small-pox will differ materially according to the species of the disease. In the distinct, ushered in by synochal pyrexia, it may be occasionally proper in persons of a middle age, good constitution, and plethoric habit, to begin by taking away a moderate quantity of blood; the exhibition of an emetic will be generally advisable, provided there be no material tenderness of the stomach; the bowels must then be cleared, antimonial and other diaphoretics employed, and the antiphlogistic regimen strictly enforced. It is particularly useful in this disease during the eruptive fever to expose the patient freely to cold air, as taught by the celebrated Sydenham; and even the cold affusion may be proper where there is much heat and redness of the skin, unless the lungs be weak. After the eruption has come out, the symptoms are usually so much mitigated that little medical interference is necessary. But the confluent small-pox requires more management; after evacuating the primæ viæ, and employing other means to moderate the fever in the beginning, the severalremedies adapted to support the strength and counteract the septic tendency, must be resorted to as the disease advances. The chief points of difference are, that bark may be more freely given to promote the process of suppuration, and opium to relieve the irritation in the skin; when the eruption has come out it will be generally proper to direct a full dose of this remedy every night to procure rest, using proper precautions to obviate its confining the bowels, or determining to the head. Where alarming convulsions occur also, opium is the medicine chiefly to be relied upon, taking care subsequently to remove any source of irritation from the prima viæ. Sometimes the tepid bath may be useful under these circumstances, and favor the ap

pearance of the eruption, where the skin is pale and cold, the pulse weak, &c. Where at a more advanced period the pustules flatten, and alarming symptoms follow, the most powerful cordial and antispasmodic remedies must be tried, as the confectio opii, æther, wine, &c. For the relief of the brain, or other important part particularly affected, local means may be used as in typhus. To prevent the eyes being injured, a cooling lotion may be applied, and blisters behind the ears, or even leeches to the temples.

VARIOLA VACCINA, or Cow-Pox, the name commonly given to a very singular disease which has occupied a great share of the attention of medical men. It has been many years prevalent in some of the great dairy counties in England, particularly Gloucestershire; and it has been long understood by the farmers and others in these counties, that it for ever exempts all persons who have been infected with it from the contagion of small-pox. Dr. Jenner was the first person who made this fact practically certain, by introducing the vaccine innoculation. The following is an abstract of his account of the distemper:-"There is a disease to which the horse is frequently subject. The farriers have termed it the grease. It is an inflammation and swelling in the heel, discharging matter. In the dairy county of Gloucestershire a great number of cows are kept, and the office of milking is performed indiscriminately by men and maid servants. One of the former having been appointed to apply dressings to the heels of a horse affected with the grease, incautiously bears his part in milking the cows with some particles of the infectious matter adhering to his fingers. When this is the case, it commonly happens that a disease is communicated to the cows, and from the cows to the dairy maids, which spreads through the farm until most of the cattle and domestics feel its unpleasant consequences. This disease has obtained the name of the cow-pox. It appears on the nipples of the cows in the form of irregular pustules. At their first appearance they are commonly of a palish blue, or rather of a color somewhat approaching to livid, and are surrounded by an erysipelatous inflammation. These pustules, unless a timely remedy be applied, frequently degenerate into phagedenic ulcers, which prove extremely troublesome. The animals become indisposed, and the secretion of milk is much lessened.' That this disease originates with the horse has been disputed; but, as the fact is by no means ascertained, the arguments on both sides are of minor importance. The great question to be determined is, whether this disease, when communicated to the human subject, prevents the possibility of future infection from small-pox; and, happily, the weight of evidence arising from the experience of several years' universal practice, leaves little reason to doubt that it does, although some medical men of eminence persist in a contrary opinion. The following remarks will be of use to the practitioner. It is of the utmost consequence that the matter employed should be the genuine vaccine virus. Dr. Jenner points out the following particulars as sources of a spurious cow-pox: 1. That arising from pustules on the nipples or

3.

udder of the cow, which pustules contain no specific virus. 2. From matter, although originally possessing the specific virus, which has suffered a decomposition, either from putrefaction, or any other cause less obvious to the senses. From matter taken from an ulcer in an advanced stage, though the ulcer arose from a true cowpox. 4. From matter produced on the human skin from the contact of some peculiar morbid matter degenerated by a horse. Many have remarked that inoculation with the vaccine matter is more apt to fail in communicating the infection than with variolous matter, especially if it be suffered to dry upon the lancet before it is used. Care should therefore be taken to moisten it a considerable time before it is used. Danger may arise from mistaking the local effects of the vaccine disease for its effects upon the constitution. To guard practitioners against this error, Dr. Woodville makes the following remarks:- When a considerable tumor and an extensive redness takes place at the inoculated part, within two or three days after the infectious matter has been applied, the failure of inoculation may be considered as certain, as where neither redness nor tumor is the consequence. This rapid and premature advancement of the inflammation will always be sufficient to prevent the inoculator from mistaking such cases for those of efficient inoculation. But there are other circumstances under which I have found the inoculation to be equally ineffectual, and which, as being more likely to deceive the inoculator, require his utmost circumspection and discrimination. I here allude to cases in which it happens that though the local affection does not exhibit much more inflammation than is usual, yet neither vesicle nor pustule supervenes; and in which, about the sixth or seventh day, it rapidly advances into an irregular suppuration, producing a festering or crustaceous sore. Care, however, should be taken to distinguish this case from that in which the inoculated part assumes a pustular form, though it continues for one or two days only, when the same appearances follow as those above described; for I have experienced the latter inoculation to be as effectual as where the tumor has proceeded in the most regular manner. The efflorescence at the inoculated part, which seldom intervenes before the eighth, or later than the eleventh day, is to be regarded as an indication that the whole system is affected; and, if the patient has not felt any indisposition on or before its approach, he may be assured that there will not be any afterwards. When efflorescence does not commence till the eleventh day, it is almost always attended with more indisposition than when it occurs on the eighth or ninth day. The efflorescence is more frequent in young infants than in children advanced to three or four years of age; and the former have the efflorescence and the disease more favorably than the latter, insomuch that by far the greater part of them have no perceptible illness, and require no medicines. On the other hand, in adults the cow-pox frequently produces head-ache, pain of the limbs, and other febrile symptoms, for two or three days, which are greatly relieved by a brisk purgative.'

VARNISH, a clear limpid fluid, capable of nardening without losing its transparency, used by painters, gilders, &c., to give a lustre to their works, to preserve them and defend them from the air. A coat of varnish ought to possess the following properties:-1. It must exclude the action of the air; because wood and metals are varnished to defend them from decay and rust. 2. It must resist water; for otherwise the effect of the varnish could not be permanent. 3. It ought not to alter such colors as are intended to be preserved by these means. Resins are used as the basis of varnish. Resins may be dis solved by three agents. 1. By fixed oil. 2. By volatile oil. 3. By alcohol. And accordingly we have three kinds of varnish: the fat or

oil varnish, essential varnish, and spirit varnish. Before a resin is dissolved in a fixed oil, it is necessary to render the oil drying. For this purpose the oil is boiled with metallic oxides; in which operation the mucilage of the oil combines with the metal, while the oil itself unites with the oxygen of the oxide. To accelerate the drying of this varnish, it is necessary to add cil of turpentine. The essential varnishes consist of a solution of resin in oil of turpentine. The varnish being applied, the essential flies off and leaves the resin. This is used only for paintings. When resins are dissolved in alcohol, the varnish dries very speedily, and is subject to crack; but this fault is corrected by adding a small quantity of turpentine to the mixture, which renders it brighter, and less brittle when dry.

The following are the ingredients in different varnishes:- For toilet-boxes, cases, fans, &c.Dissolve two ounces of gum mastich, and eight ounces of gum sandarach, in a quart of alcohol; then add four ounces of Venice turpentine. For wainscots, cane-chairs, iron-chairs, grates.—Dissolve, in a quart of alcohol, eight ounces of gum sandarach, two ounces of seed lac, four ounces of resin; then add six ounces of Venice turpentine. For fiddles, &c.-Put four ounces of gum sandarach, two ounces of lac, two ounces of gum mastich, one ounce of gum elemi, into a quart of alcohol, and hang them over a slow fire till they are dissolved; then add two ounces of turpenDissolve in a quart of alcohol six ounces of tine. To employ vermilion for painting equipages. sandarach, three ounces of gum lac, and four ounces of resin; afterwards add six ounces of turpentine. Gold-colored varnish.-Pound separately four ounces of stick lac, four ounces of gamboge, four ounces of dragon's blood, four ounces of anotta, and one ounce of saffron put each of them separately into a quart of alcohol, and expose them for five days in a narrowmouthed bottle to the sun, or in a very warm room, shaking them frequently. When all are melted mix them together. In order to make silver imitate gold exactly when covered with this varnish, the quantity of ingredients must be somewhat greater. The method of gilding silver-leaf, &c., with this varnish, is as follows:The silver-leaf being fixed on the subject in the same manner as gold leaf, by the interposition of proper glutinous matters, the varnish is spread upon the piece with a brush or pencil. The first coat being dry, the piece is again and again washed over with the varnish till the color appears sufficiently deep. What is called gilt leather, and many picture frames, have no other than this counterfeit gilding. For plain frames thick tin-foil may be used instead of silver. The tin-leaf, fixed on the piece with glue, is to be burnished, then polished with emery and a fine linen cloth, and afterwards with putty applied in the same manner: being then lacquered over with varnish five or six times, it looks very nearly like burnished gold. The same varnish, made with a less proportion of the coloring materials, is applied also on works of brass. Oil varnishes.-Gum, copal, and amber, are the substances principally employed in oil varnishes;