Bahama Islands are not so large; these, however, are frequently four feet in diameter, and rising to a great height, notwithstanding they are generally found on the solid rock, where there seems to be scarcely any earth for their nourishment. The wood brought from the Bahama Islands has usually passed under the name of Madeira wood; this the Spaniards make great use of for building ships; it is better adapted to this purpose than most sorts of wood yet known, being very durable, resisting gun shots, and burying the shot without splintering. The excellency of this wood for all domestic purposes, has been long known in England.

**SWIMMING, the art, or act, of sustaining the body in water, and of moving therein; in which action the air-bladder and fins of fishes bear a considerable part. Some have supposed, that the motion of fish in the water depends principally upon the pectoral fins, but the contrary is easily proved by experiment; for if the pectoral fins of a fish are cut off, and it be again put into the water, it will be found to move forward or sideways, upward or downward, as well as it did when it had them on. If a fish be carefully observed, while swimming in a basin of clear water, it will be found not to keep these pectoral fins constantly expanded, but only to open them at such times as it would stop or change its course; this seeming to be their principal, if not their only use. The pectoral and ventral fins, in the common fishes of a compressed form, serve in the same manner in keeping the fish still, and serve in scarce any other motion than that towards the bottom; so that this motion of the fish, which has been generally attributed to their fins, is almost wholly owing to their muscles, and the equipoise of their airbladder. That the use of the pectoral and ventral fins is to keep the fish steady and upright in the water, is evident from the consequences of their loss: if they are cut off, and the fish put again into the water, it cannot continue in its natural erect posture, but staggers about, and rolls from side to side. The fins of the back and anus are also of great use to the keeping the creature in its natural position, as is easily seen by cutting them off, and observing the motions of the fish afterwards. Though a great deal depends on the motion of the muscles of the several parts of the body, in the swimming of the fish, yet the tail, and those muscles which move the lower part of the VOL. VI.

body, to which it is affixed, are the great instruments by which their swift motions in the water are performed. The moving the tail, and that part of the body to which it adheres, backward and forward, or sideways any one way, throws the whole body of the fish strongly the contrary way; and even in swimming strait forward, the motion and direction are both greatly assisted by the vibrations of this part, as may be experienced in the motion of a boat, which, when impelled forward, may be firmly guided by means of an oar held out at its stern, and moved in the water as occasion directs. The dorsal muscles, and those of the lower part of the body, between the anus and tail, are the principal that are used in the motion of this part, and these

are therefore the most useful to the fish in swimming. The muscles of the belly seem to have their principal use in the contracting the belly and the air-bladder. They have been supposed of use to move the belly-fins; but there are too many of them for such a purpose, and these fins have each its peculiar muscle, fully sufficient to the business. The use of the tail in swimming is easily seen, by cutting it off, and committing the fish to the water without it, in which case it is a most helpless creature.

Brutes swim naturally, but men attain this art by practice and industry: it consists principally in striking alternately with the hands and feet; which, like oars, row a person forward: he must keep his body a little oblique, that he may the more easily erect his head, and keep his mouth

above water.

We shall here insert some maxims on the art of swimming that may be useful, and which are said to have been written by the late Dr. Franklin.

1. That though the legs, arms, and head of a human body, being solid parts, are specifically something heavier than fresh water, yet the trunk, particularlythe upper part, from its hollowness, is so much lighter than water, as that the whole of the body, taken together, is too light to sink wholly under water, but some part will remain above, until the lungs become filled with water; which happens from drawing water into them instead of air, when a person, in the fright, attempts breathing, while the mouth and nostrils are under water. 2. That the legs and arms are specifically lighter than salt water, and will be supported by it, so that a human body would not sink in salt water, though the lungs were filled as

5.

above, but from the greater specific gravity of the head. 3. That therefore a person throwing himself on his back in salt water, and extending his arms, may easily lie so as to keep his mouth and nostrils free for breathing; and, by a small motion of his hands, may prevent turning, if he should perceive any tendency to it. 4. That in fresh water, if a man throws himself on his back, near the surface, he cannot long continue in that situation, but by proper action of his hands on the water. If he uses no such action, the legs and lower part of the body will gradually sink till he comes into an upright position, in which he will continue suspended, the hollow of the breast keeping the head uppermost. But if in this erect position, the head is kept upright above the shoulders, as when we stand on the ground, the immersion will, by the weight of that part of the head that is out of water, reach above the mouth and nostrils, perhaps a little above the eyes, so that a man cannot long remain suspended in water with his head in that position. 6. The body continuing suspended as before, and upright, if the head be leaned quite back, so that the face looks upwards, all the back part of the head being then under water, and its weight consequently in a great measure supported by it, the face will remain above water quite free for breathing, will rise an inch higher every inspiration, and sink as much every expiration, but never so low as that the water may come over the mouth. 7. If therefore a person, unacquainted with swimming, and falling accidentally into the water, could have presence of mind sufficient to avoid struggling and plunging, and to let the body take this natural position, he might continue long safe from drowning, till perhaps help would come. For as to the clothes, their additional weight while immersed is very inconsiderable, the water supporting it; though when he comes out of the water, he would find them very heavy indeed. The subject has within the last two or three years been investigated in Nicholson's Philosophical Journal, whence it should seem, that if a person could have sufficient presence of mind never to raise his hands above water, he could not sink.

SWIVEL, in gunnery, a small piece of artillery carrying a shot of half a pound weight, and fixed in a socket on the top of a ship's side, stern, or bow, and also in the tops; the trunnions of this piece are contained in a sort of iron crotch, the lower end of which terminates in a cylindrical pi

vot, resting in the socket so as to support the weight of the cannon. By means of this swivel, which gives name to the piece of artillery, and an iron handle, the gun may be directed by hand to any object.

SWORD, an offensive weapon, worn at the side, and serving either to cut or stab. Its parts are the handle, guard, and blade; to which may be added the bow, scabbard, pummel, &c. Fencing masters, however, divide the sword into the upper, middle, and lower part; or the fort, middle, and foible.

SYENA, in botany, a genus of the Triandria Monogynia class and order. Essen. tial character: calyx three-leaved; petals three; anthers oblong; capsule one-celled, three-valved. There is only one species, viz. S. fluviatilis. This is a minute mossy plant; stem somewhat branched, decumbent; leaves capillaceous, in whorls; flowers axillary, white, peduncled, solitary. It is a native of Guiana, in rivulets.

SYLLABLE, in grammar, a part of a word, consisting of one or more letters, pronounced together.

According as words contain one, two, three, four, &c. syllables, they are denomi. nated monosyllables, bissylables, trisylla bles, tetrasyllables, polysyllables, &c. and the division of a word, into its constituent syllables, is called spelling.

SYLLABUS, in matters of literature, denotes a table of contents, or an index of the chief heads of a book or discourse.

SYLLOGISM, in logic, an argument or term of reasoning, consisting of three propositions; the two first of which are called premises, and the last the conclusion. Syllogisms are nothing but the expressions of our reasonings, reduced to form and method: and hence, as every act of reasoning implies three several judgments, so every syllogism must include three distinct propositions. Thus, in the following syllo. gism :

Every creature possessed of reason and liberty is accountable for his action. Man is a creature possessed of reason and liberty:

Therefore man is accountable for his actions.

We may observe that there are three several propositions, expressing the three judgments implied in the act of reasoning: the two first propositions answer the two previous judgments in reasoning, and are hence called premises; as being placed before the other, which is termed the conclusion. We are also to remember, that the terms expressing the two ideas whose relation we inquire after, as here, "man"

and "accountableness," are in general called the extremes; and that the intermediate idea, by means of which the agreement or disagreement of the two extremities is traced, viz. "a creature possessed of reason and liberty," takes the name of the middle term. Hence, by the premises of a syllogism, we are always to understand the two propositions, where the middle term is severally compared to the two extremes; for these constitute the the previous judgments, whence the truth we are in quest of, is by reasoning deduced. The conclusion is, that other proposition, in which the extremes themselves are joined or separated, agreeably to what appears upon the above comparison. As, therefore, the conclusion is made up of the extreme terms of the syllogism; so that extreme, which serves as the predicate of the conclusion, goes by the name of the major term; and the other term, or subject of the conclusion, is called the minor term. From this distinction of the extremes arises also a distinction between the premises; that proposition, which compares the greater extreme with the middle term being called the major propo sition; and the other, where the lesser extreme is compared with the middle term, being called the minor proposition. In a single act of reasoning, the premises of the syllogism must be self-evident truths, otherwise the conclusion could not follow. For instance, in the major of the above mentioned syllogism, viz.“ every creature possessed of reason and liberty is accountable for his actions," if the connection between the subject and predicate could not be perceived by a bare attention to the ideas themselves, the proposition would require a proof itself; in which case, a new middle term must be sought for, and a new syllogism formed to prove the said major and should it so happen, that in this second essay there was still some proposition, whose truth did not appear at first sight, recourse must be had to a third syllogism to prove it. And when, by conducting our thoughts in this manner, we at last arrive at some syllogism, where the premises or previous propositions are intuitive, or self-evident truths, the mind then rests in full security, as perceiving that the several conclusions it has passed through, stand upon the immoveable foundation of self-evidence, and when traced to their source, terminate in it. The great art lies, in so adjusting our syllogisms to one another, that the propositions severally made use of as premises, may be manifest consequences of what goes be

fore, so as to form one connected demon

stration.

With respect to the different forms or figures of syllogisms, it frequently hap pens that the middle term is the subject of the major term, and the predicate of the minor; but though this disposition of the middle term be the most natural and obvious, it is not, however, necessary; since the middle term is often the subject of both the premises, or the predicate in both; and sometimes it is the predicate in the major, and the subject in the minor proposition. Now this variety in the or der and disposition of the middle term, constitutes what logicians call the forms or figures of syllogism.

But besides this distinction of syllogisms into different figures, there is also a further subdivision of them in every figure, called modes, or moods. See MOOD.

These distinctions of syllogism, accord. ing to figure and mood, respect chiefly simple syllogisms, or those limited to three propositions, all simple; and where the extremes and middle term are connected immediately together. But as the mind is not tied down to any one form of reasoning, but sometimes makes use of more, sometimes of fewer premises, and often takes in compound and conditional propositions, there hence arises other distinctions of syllogisms.

When in any syllogism the major is a conditional proposition, the syllogism itself is termed conditional. Such is the following one:

If there is a God, he ought to be wor-
shipped;

But there is a God:
Therefore he ought to be worshipped.

In syllogisms of this kind, the relation between the antecedent, or the conditional part," if there is a God," and the consequent, "he ought to be worshipped," must ever be real and true; that is, the antecedent must always contain some certain and genuine condition, which necessarily implies the consequent; otherwise the proposition itself will be false, and therefore ought not to be admitted into our reasonings. There are two kinds of conditional syllogisms, one of which is called in the schools modus ponens; because from the admission of the antecedent they argue to the admission of the consequent, as in the syllogism above: the other is called modus tollens, because in it both antecedent and consequent are rejected, as in the following syllogism:

If God were not a being of infinite goodness, neither would he consult the happiness of his creatures; But God does consult the happiness of his creatures;

Therefore he is a being of infinite good

ness.

Again, as from the major's being a conditional proposition, we obtain conditional syllogisms; so, where it is a disjunctive proposition, the syllogism is also called disjunctive, as in the following example:

The world is either self-existent, or the work of some finite, or some infinite being.

But it is not self-existent, nor the work of a finite being :

Therefore it is the work of an infinite being.

Now a disjunctive proposition is that, where, of several predicates, we affirm one necessarily to belong to the subject, to the exclusion of all the rest, but leave that particular one undetermined; hence it follows, that as soon as we determine the particular predicate, all the rest are to be of course rejected; or if we reject all the predicates but one, that one necessarily takes place. When, therefore, in a disjunctive syllogism, the several predicates are enumerated in the major, if the minor establishes any one of these predicates, the conclusion ought to remove all the rest; or if, in the minor, all the predicates but one are removed, the conclusion must necessarily establish that

one.

In the several kinds of syllogisms hitherto mentioned, we may observe, that the parts are complete; that is, the three propositions of which they consist are expressed in form. But it often happens, that some one of these premises is not only an evident truth, but also familiar, and in the mouths of all men; in which case it is usually omitted, whereby we have an imperfect syllogism, that seems to be made up of only two propositions : such is the following one :

Every man is mortal;

Therefore every king is mortal.

Here the minor proposition, "every king is man," is omitted, as being so clear and evident, that the reader may easily supply it.

SYLVAN, in mineralogy, a genus which is divided into four species; viz. 1. "The native sylvan," of which the colour

Before the blow-pipe it melts as easily as lead, emits a thick white smoke, and burns with a light green colour, and a sharp disagreeable odour. When exposed to a low heat, it is converted into an oxide: by an increase of temperature, it melts into a brownish black glass, in, which gold grains are interspersed at a still bigher heat, the oxide is completely vola tilized. It occurs in veins, and is accompanied with iron pyrites, blende lead-glance, quartz, and lithomarge, and is found in blance to antimony, and was formerly callTransylvania. It bears a strong resemed "aurum problematicum:"-" white gold ore," &c. It was denominated Jameson, who thinks it more expressive "sylvan" by Kirwan, and is so called by than "tellurium," a name proposed by Klaproth.

2. "Graphic ore," which is likewise found in Transylvania: it is worked as an ore of gold, and bas obtained the name of graphic gold: it consists of