073 



SOLSTICES. 



SOMNAMBULISM. 



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It consists of two parts. The first part (chap, i.-ix.) contains the 

 praise of wisdom, an exhortation to all, and especially to kings, to seek 

 it, and the manner in which it is to be obtained. The second part 

 (chap, x -xix.) brings forward examples from history of the happiness 

 that springs from wisdom and the misery entailed by folly. Through- 

 out the book Solomon is represented as speaking; and the work is 

 evidently an imitation of his proverbs. It is remarkable as being the 

 earliest Jewish work extant which contains a clear statement of the 

 doctrine of rewards and punishments in a future state. 



SOLSTICES, the points of the ecliptic which are highest above the 

 equator, at which, the sun's motion in declination being imperceptible, 

 the days remain sensibly unaltered in length for several days together, 

 as they would do if the sun absolutely stood still : whence the nrvme. 



[SUN.J 



SOLUBILITY. [SOLUTION.] 



SOLUTION. When the force of ADHESION is exerted between a 

 solid and a liquid with sufficient energy to overcome the cohesion of 

 the former, the substance is said to be soluble, or to undergo solution, 

 or to be dissolved. The solution of sugar in water, of resin in spirits 

 of wine, of silver in mercury, is now regarded as a form of adhesion. 

 Certain liquids are also soluble in other liquids, gases in other gases, 

 and gases in liquids, as noticed under DIFFUSION. For the solubility 

 of gases in liquids, we refer to GAS. In the present article we may 

 give a few details respecting the solution of solids in liquids. 



The liquid which effects the solution is usually termed the solvent, 

 but sometimes the menstruum. Particular solutions have also special 

 names, such as syrup, which is applied to the solution of sugar in 

 water, while tincture refers to a solution of a solid in alcohol. When a 

 liquid can no longer dissolve further portions of the solid, it is said to 

 be taturatid ; that is, the force of cohesion balances that of adhesion. 

 Generally, however, an elevation of temperature, by diminishing cohe- 

 sion, will increase the solvent powers of the liquid. But there are cases 

 in which cold appears to favour solution : thus lime and some of its 

 salt* dissolve more readily in water just above the freezing-point than 

 when boiling. Crystallised sulphate of soda requires about ten times 

 its weight of ice-cold water for solution, and its solubility increases 

 rapidly with the temperature up to 91 Fahr., from which point up to 

 the boiling-point of the solution the solubility decreases ; and the 

 liquid, saturated at 91, deposits a portion of the salt by increasing the 

 temperature. Seleniate of soda and sulphate of iron afford similar 

 results, which are due probably to the fact that heat diminishes 

 adhesion as well as cohesion, but the former force decreases more 

 rapidly than the latter. If a liquid added to a solution have a stronger 

 adhesion to the solvent than to the substance dissolved, the latter will 

 often be thrown down in a pulverulent state : thus, the addition of 

 water to camphorated spirit will throw down camphor. 



Solution is favoured by increasing the extent of surface in the solid, 

 as by reducing it to powder. In general, the first portions of a solid 

 disappear rapidly, and the after portions more and more slowly until 

 saturation is reached. Solids present innumerable degrees of solubility ; 

 for while some bodies, such as sulphate of baryta, are almost insoluble, 

 and sulphate of lime only soluble in about the proportion of 1 part in 

 700 parts of water, 1 part of sulphate of potash will dissolve in 16 

 parts of water, and 2 parts of sulphate of magnesia will dissolve in only 

 3 of water. It is remarkable that water saturated with one salt will 

 dissolve others. As aqueous solutions of .solids are heavier than water, 

 the degree of solubility of a solid may be judged of by suspending it in 

 a glass of water, and watching the current as it descends. " If it fall 

 rapidly, and in dense strife, it will indicate rapid solubility, and the 

 formation of a dense solution ; if it fall in a very narrow stream, it will 

 indicate only moderate or slight solubility ; and by its descending 

 rapidly or in a slow broad stream, or by resting about the substance, a 

 judgment may be made of the comparative density of the solution 

 produced. If no descending current appear, nor any fluid round the 

 substance of a refractive power or colour different to that of the water, 

 then the body must be very nearly, if not quite, insoluble at common 

 temperatures." (Faraday, 'Chemical Manipulation.') The taste will ; 

 also frequently give an indication of the solubility of a solid. 



In general, a solution due to adhesion partakes of the properties 

 both of the solvent and of the substance dissolved. Where chemical 

 change intervenes, we have the properties of a third body. Hence, hi 

 cases of simple solution, the solvent and the body dissolved have, to 

 some extent, properties in common, as when mercury dissolves many 

 of the metals, and oils dissolve fatty bodies and each other ; but in 

 cases of chemical action, the affinities are strongest between bodies the 

 most dissimilar, as when the acids dissolve metals or their oxides, oils 

 the alkalies, and so on. 



The uses of solution are numerous. It allows a body to be purified 

 by filtration or crystallisation, so that one substance may be separated 

 from another, either by crystallisation or by the use of such fluids in 

 succession as have a solvent power over one or more of the substances 

 present. By means of solution, substances are prepared for the exertion 

 of chemical action, and all obstructions due to the attraction of aggre- 

 gation removed. 



SOLUTION. (Mathematics.) By the solution of a problem should 

 be meant the method of finding that which the problem requires to be 

 f. mud : but the word is frequently understood to apply to the answer 



ARTS AP SCI. DIV. VOL. VII. 



A solution is given when the problem is reduced to any other which 

 was supposed to be known before the first was presented : the difficulty 

 peculiar to the given problem is removed as soon as it is shown to be 

 capable of reference to another and a lower class. Thus, though 

 properly speaking a problem is not solved until the answer is 

 presented in numbers, yet it is not thought necessary to require that 

 such a result should be attained, provided the steps which are left are 

 such as are well known and generally admitted. Thus an equation 

 would be said to be solved were it found that the roots required are 

 those of a given quadratic ; for no one is supposed ignorant of the 

 mode of then finding them. 



A geometrical solution, in the strict sense of the word, is one in 

 which only the means of construction admitted by Euclid, or others 

 deducible from them, are employed in its attainment. This is the least 

 finished of all solutions ; for a mode of laying down the various points 

 which terminate lines is not, generally speaking, a mode of ascertaining 

 the ratio of these lines. Nor must it be forgotten by the admirers of 

 geometry that the most important part of a result, the expression of 

 the ratios which the answer bears to the several data, is only indirectly 

 obtained in their favourite method. 



When more means than those allowed by Euclid are employed, the 

 solution used to be called mechanical. It is rarely that such a solution 

 is now employed. 



An algebraical solution is one which employs algebra and arithmetic, 

 to the exclusion of geometrical construction ; that is, one in which the 

 answer can always be directly calculated from a formula. Geometrical 

 construction may be necessary for the demonstration of the solution : 

 it is enough that the answer contain no directions to find lines or 

 surfaces by construction. 



An approximate solution is one which has an amount of inaccuracy 

 necessarily. Thus if 3 + V2 were the root of an equation, this solu- 

 tion would not be called approximate ; for though \J 2 cannot be 

 perfectly represented in a finite form, the symbol itself contains the 

 mode of attaining the result with any degree of exactness short of 

 perfection. But if \J 2 were found to five decimal places, the answer 

 1'41421 would be called an approximate answer. Most solutions must 

 terminate in an approximate representation. [TRANSCENDENTAL.] 



SOLVENT. [SOLUTION.] 



SOMNAMBULISM, a word of modern origin, which means strictly 

 and etymologically sleep-iralking ; it is however generally used in a 

 more extended signification to comprehend all the phenomena that 

 take place when a person, apparently insensible to external objects, 

 acts as if he were in a state of consciousness : and this is the sense 

 which the word will bear in this article. M. Bertrand, in his ' Traite 

 du Somnambulisme ' (8vo., Paris, 1823), divides those phenomena into 

 four classes : 1, essential (or proper) somnambulism, which arises from 

 some particular disposition of the nervous system in persons who in 

 other respects apparently enjoy perfect health ; 2, symptomatic (or 

 morbid) somnambulism, which occurs in the course of certain diseases; 

 3, artificial somnambulism, which is occasioned by the proceedings 

 employed in animal magnetism or mesmerism ; and, 4, ecstatic som- 

 nambulism, which is the result of a sort of religious enthusiasm. The 

 same division of the subject will be here adopted. 



I. E'tential (or Proper) Somnambulism is intimately connected with 

 the subject of sleep and dreaming ; and in fact " a somnambulator." 

 as Dr. Pritchard says, " is nothing but a dreamer who is able 

 to act his dreams." [ DREAMS. ] [ SLEEP, in NAT. HIST. DIV. ] 

 As a minute inquiry into the physiology of these two pheno- 

 mena would here be out of place, the reader must consult the 

 articles already given on these subjects. This form of somnambulism 

 was noticed by the ancients. The author of the treatise ' De Morbo 

 Sacro,' that commonly goes under the name of Hippocrates, says that 

 " he knew many persons who used to groan and cry out in their sleep, 

 and others that seemed to pant for breath (-jrviyo^evous), and others 

 that would get up and run out of the house and act like madmen till 

 they were awakened, after which they were in good health and sound 

 sense as before, only rather pale and weak" (torn, i., p. 588, ed. 

 Kiihn). Aristotle tells us that "there are individuals who rise in their 

 sleep and walk about, seeing as clearly as those that are awake." Dio- 

 genes Laertius mentions (' De Vitis Philosophorum, Pyrrho,' lib. ix.) 

 that a Stoic philosopher named Theon was a sleep-walker ; and Galen 

 says (' De Motu Musculorum,' lib. ii., cap. 4, torn, iv., p. 435, 436, ed. 

 Kuhn) that he would not believe that people ever fell asleep while 

 walking, until one night when walking along the road he did so him- 

 self, and went on for about a furlong, sleeping and dreaming, till at 

 last he was awakened by kicking against a stone. " And this," adds 

 he, " is the reason why people cannot go on walking for any distance 

 in their sleep, because they cannot meet with a perfectly smooth 

 road;" in which he is not quite correct, aa we often find that both the 

 bodily and intellectual powers of the individual are more active and 

 developed in his sleep then when he is aw,ake, and that he is then able 

 to perform feats which at any other time he would shudder at. The 

 instances on record of this species of somnambulism are so numeroun 

 that it is difficult to select the most interesting ; one or two examples 

 however must be given, and for a more copious collection the reader 

 must be referred to some of the works whose titles will be given in the 

 following part of this article. 



Several interesting cases of somnambulism will be found in Mura- 



