SOLAN UJC DULCAMARA. 



SOLAR ECLIPSE. 



SOLATIUM UULCAMA'RA, an indigenous perennial climbing plant, 

 common in wet and shady place*, especially hedge*. It has a remark- 

 ably xigsag item, with alternate team, the lower ones lanceolate, 

 entire, the upper hastate ; the flowen resemble thorn of the potato, 

 bat are smaller, and are succeeded by a cluster of red berries. Thin 

 plant is called woody nightshade, to distinguish it from the Alropa 

 Mladonxu, or drodty nightshade. The yonng twigs or tope are officinal, 

 and they should be gathered in spring, before the (lowering of the 

 plant, or in autumn while the leares are yet frttk, as much activity 

 seems to belong to the leaves, and the twigs are beat from plants about 

 three years old. When fresh, the plant has an unpleasant odour, 

 which is in a great measure lost by drying, aa is also a large portion 

 of water. The taste is at Ant bitter' and slightly acrid, then sweet ; 

 hence the name kiiltr-ttrerl given to it, 



Ten pounds of the dried twigs yield two pounds of extract Accord- 

 ing to Pfaff. 100 pounds of perfectly dried sterna yield a bitter-sweet 

 extractive (picroglycion), 21 ; vegeto-animal matter, 3 ; gummy extrac- 

 tive, 12 ; gluten with wax, 1 ; ream with benzoic acid, 2 ; gum, 

 starch, salts (chiefly of lime), 6; and woody fibre, 62. Solanina 

 (solania) has been found by Desfoaws. Whether picroglycion, called 

 also dulcamarin, and dulcarin, is a distinct principle, or combination 

 of solanina with sugar, is doubtful. 



Bitter-sweet, when taken fresh, has a slightly narcotic influence, 

 causing also nausea, vertigo, and a dryness of throat, like other solana- 

 ceous poisons. If delirium display itself, it is always of a most frantic 

 kind. Perspiration or an increased discharge of mine generally occurs, 

 followed by gentle purging. 



Bitter-sweet is chiefly employed in cutaneous diseases, especially of 

 the scaly kind, such aa lepra ; it may be given internally, while a strong 

 wash of it is applied externally. It is also useful in some vesicular 

 diiMuM, such as herpes and eczema. In these its virtues as an 

 external application may be increased by dissolving in it sulphuret 

 of potass. This combination relieves most effectually the intolerable 

 irritation of these complaints. 



It is usually ordered in the form of decoction, but long boiling is 

 destructive of its powers. Slow simmering is preferable. The 

 extract, when prepared from the fresh plant with a low degree of heat, 

 is a good form for internal administration, as it may be combined 

 with antiiiKini.il*. 



In cases of poisoning by the berries, often mistaken for currants, 

 the stomach-pump should be used aa speedily as possible, and moderate 

 venesection is of service. 



SOLAR CYCLE. [PERIODS OF REVOLUTION.] 



SOLAR ECLIPSE. The phenomena of an eclipse of the sun 

 resemble those of the moon in one respect only, namely, that the body 

 of the luminary disappears. In all other respects there is so great a 

 difference, both in the cause of the phenomenon and its attendant 

 circumstances, that it is a pity one term, eclipse, should be used in 

 senses so different. In the first place, the disappearance of the moon 

 arises from the earth intercepting the light which she ought to receive, 

 while that of the sun is the consequence of the moon coming between 

 the nun and the earth. The body of the moon is never absolutely 

 hidden, and is even slightly visible through a telescope during the 

 darkest eclipse : but the body of the sun is really hidden by the inter- 

 vention of the opaque substance of the moon. Again, the phenomena 

 of an eclipse of the moon are the same for every point of the earth at 

 which they are visible : the beginning, middle, and end of the 

 phenomenon happen at the same instant of absolute time everywhere, 

 and the same portion of the moon is hidden from all the earth at the 

 same instant. But in a solar eclipse, it entirely depends upon the 

 position of the spectator whether there is any eclipse at all ; and of 

 two persons at different parts of the earth, at the same instant, one 

 may see the sun totally eclipsed, while the other may, by the bright- 

 ness of the sun's rays, not know that the moon is almost close to him. 

 A screen held before a candle may be an eclipse of the candle for one 

 person in the room, but not for another, on account of their difference 

 of place ; this is an illustration of the solar eclipse : a ball thrown into 

 a dark corner may be invisible to all the persons in a room at the same 

 time ; this is the same illustration of a lunar eclipse. 



If the earth had no motion of rotation, the inhabitants of any one 

 place would see something exactly resembling a lunar eclipse ; the sun 

 being in place of the moon, and the moon in place of the earth's 

 shadow. But different places would see different kinds of eclipses, 

 some losing more of the sun's body, and others less. The rotation of 

 the earth, without materially altering the character of the phenomenon, 

 make* it much more difficult to calculate : for it is as if each spot of 

 the earth, instead of standing still to witness one phmonxBon, or one 

 simple eclipse, were constantly taking into view portions of different 

 phenomena, a part of one followed by a subsequent part of another. 

 In an eclipse of the moon, whatever may be the phase for the time 

 being, from the disappearance of the first to the reappearance of the 

 last edge, the only question as to whether such phase will In- 

 visible or not at any place is the following : Will the moon !> 

 the horizon at that place when the phase occurs 1 Suppose, for instance, 

 it were asked, what place* on the earth will see the beginning of the 

 eclipse, the disappearance of one edge of the moon, at the instant when 

 the moon rises I The answer is, calculate the absolute instant of the 

 beginning of the eclipse, find out the spot to which the moon is vertical 



at that instant, and all place* 00* distant from it will be exactly in the 

 same predicament with respect to the eclipse. But in an eclipse of the 

 mm, the beginning at two different place* does not happen at the same 

 instant; the inhabitants of any the same circle see very u 

 phases, and a line drawn through all the places which nee tin 

 sort of phase under the same position of the luminaries with respect to 

 their horizons, will be very different from a circle. Without attempting 

 to give any account of the modes of ascertaining all these points, we 

 subjoin, from the ' Nautical Almanac,' a projection of the eclipse which 

 took place on the 7th of July, 1842. 



The southern line passes through all the places which see a simple 

 contact of the luminaries and nothing more : the edges of the lumina- 

 ries unite for a moment and then separate. This line touches the two 

 end* of a large figure of eight divided by another line passing through 

 its loop ; and the portion of the earth which at any time sees a total 

 eclipse is contained in the broad shaded band. On the line marked 

 "beginning of eclipse at sunrise" live those to wh ..... tlie lumina- 

 ries rise in contact : the other lines are similarly explained. The 

 eclipse is first seen at the place marked " First contact " on the line 

 just mentioned. One point is marked as having both beginning, middle, 

 and end of the eclipse at sunrise : this means that the eclipse i 

 only a contact, so that its beginning, middle, and end take place at the 

 same moment, and that moment is sunrise. At the loop of the figure 

 of eight, the beginning, middle, and end are represented as 

 them taking place both at sunrise and sunset : which must be a mystery 

 to those who are not used to trace mathematical conceptions ( 

 limitH : are there two eclipses, one for sunrise and one for sunset ? The 

 explanation is this : there is at every moment of time a point in tin; 

 arctic regions at which the sun is making its first appearance or i 

 appearance previously or subsequent to the long polar day or nigl 

 this moment approaches the days shorten, if the disappearance be 

 coming on, and begin from nothing if the appearance be coming on : 

 the long day or night being preceded by the ordinary days or nights of 

 the rest of the earth. Now the point which is at the loop is that 

 of the earth at which the sun and moon are in contact (without any 

 further eclipse) at the moment when the sun first grazes their horizon 

 after their polar night : so that their day is but a moment, and at that 

 moment the contact takes place. 



The figure of the projection is not always like that of the preceding : 

 sometimes the loops become two ovals separated by a line which is 

 continued through the middle of them, the part of this line between 

 the ovals being a line on which nothing but a simple contact is seen. 



There is an excellent mathematical account of eclipses in general, 

 with the full mode of calculating them, and examples, by Mr. \Vool- 

 house, in the Supplement to the ' Nautical Almanac' for 1836. From 

 this we extract the summary of the limits within which an > 

 whether of the sun or moon, can happen. 



At the time of full moon an eclipse of the moon will be certain 

 when the moon's latitude is less than 51' 57", impossible when it is 

 greater than 68' 45", and doubtful between these limits. For the 

 doubtful cases an eclipse will result when the moon's latitude is less 

 than 



61 



16" 



p and i being the equatorial horizontal parallax and semi-diameter of 

 the moon, and r and a those of the sun. 



At the time of new moon an eclipse of the sun will be certain when 

 the moon's latitude is less than 1" 28' 15", impossible when it is greater 

 than 1 34' 52'', and doubtful between these limits. For the doubtful 

 cases, an eclipse will happen when the moon's latitude is less than 



^-T-KT-H-T 25". 



It is hardly necessary to state that eclipses of the sun are frequently 

 wholly partial, that is, not total for any one moment to any one part 

 of the earth. Sometimes, though the eclipse be central, it is not total 

 on account of the moon not being near enough to hide the whole of 

 the sun ; in which case part of the latter is seen as a bright ring round 

 the part hidden by the moon, and the eclipse is called annular. 



Before proceeding to give some account of the physical phen< 

 observed during total eclipses of the sun, it may be desirable to allude 

 briefly to some of tho more interesting eclipses of this nature recorded 

 in history. 



Tho ancient literature of Greece and Rome contains several inci* 

 allusions to the occurrence of total eclipses of the sun. The most 

 celebrated of these is the eclipse mentioned by Herodotus as having 

 taken place during a battle between the Medes and Lydian*. The 

 historian relates that the two hostile arm' much terrified by 



the spectacle of the eclipse, that they sudii. ''ting, 



and concluded a treaty of amity and peace. I le further >tate- that the 

 had been foretold to the lonians by Thale the Milesian. The 

 precise date of this eclipse has given rise to mn.'h iii-ru-Mon in 

 modern time*. In 1M1 the iate FraneH Haily .t, -da paper 



to the Royal Society, in which, by availing himself of Burg's lunar 

 tables, he endeavours to prove that a total eclipse of the sun which 

 occurred on the 30th of September, 610 B.C., must have liecn the one 

 alluded to by Herodotus. He acknowledges, however, that the ele- 

 ments of the lunar orbit employed in his investigation failed to 



