429 



SEAT. 



SECONDARY. 



430 



world. B is at the summer solstice, where the sun is most above the 

 equator on the northern side ; the diurnal circles north of the equator 

 have more day than night, and have their longest days : and vice rcrgfi. 

 c is the autumnal equinox, the phenomena of A being repeated. D is 

 at the winter solstice, where the sun is farthest from the equator on 

 the southern side ; the phenomena of B are now reversed, the days 

 being shortest on the north side of the equator. This figure very well 



A N 



explains the variation of days and the main reason for the phenomena 

 of seasons in the extra-tropical parts of the earth. It is evident that, 

 speaking of the northern hemisphere, the sun, being above the equator, 

 gives not only longer days, but greater altitudes ; more powerful light 

 and heat, and more of it in duration. 



The average temperature being nearly the same in different .years, 

 the northern side of the earth mast be receiving more than it parts 

 with during a portion of the year, and parting with more than it 

 receives during the remainder. The summer half of its year is that 

 half during which it gains, on the whole, more than it parts with ; the 

 surplus being that which is lost during the winter half. The day in 

 which niM-t heat is received is the longest day; but it is notorious 

 that the hottest weather is generally some time after the longest day. 

 This is easily explained, as follows : The time of the greatest heat is 

 not that at which most heat is received, but that at which the quantity 

 of heat is the greatest, namely, just before the daily receipts of heat 

 begin to fall short of the daily expenditures. So long as the receipt 

 exceeds the expenditure, heat is daily added to the hemisphere, and the 

 weather becomes hotter. The same reason may be given for the 

 greatest cold generally following the shortest day, with a considerable 

 interval. All these circumstances, however, depend much on the at- 

 mospheric circumstances of the year. 



The preceding explanation does not serve for the tropical climates, 

 the days and night* are here so nearly equal throughout the year, that 

 seasons are caused more by the effect of the wind? (which are very 

 regular, and depend mainly on the sun's position) than by changes in 

 the direct action of the sun's light and heat. The seasons are not a 

 summer and a winter, so much as recurrences of wet and dry periods, 

 two in each year. 



With regard to the quantity of heat received in a day, it might be 

 expressed, so far as it is not modified by the atmosphere, in a formula 

 depending on the latitude of the place and the sun's declination. It 

 will be enough to say that this formula shows that, the sun bcini; in 

 the equator, the day's heat in different places is as the cosine of thn 

 latitude ; and that for all places at the equator, the day's heat for 

 different days in as the cosine of the sun's declination. 



The different distances at which the earth is from the sun, at dif- 

 ferent times of the year, do not affect the heat received in a given 

 portion of the orbit. The sun is nearest to the earth in our mid- 

 winter, but for that reason the winter is shorter, since the earth moves 

 more rapidly when nearer to the sun. The compensation is exact, for 

 the quantity of heat received at any one moment, while the radius of 

 the earth's orbit moves through any small angle, is greater or less in 

 the inverse proportion of the square of that radius. But the time of 

 describing that angle is less or greater in the direct proportion of the 

 same square. Consequently the heat actually received by the earth in 

 the two halves of its orbit is the same in both. 



SKAT (in a church). [Pew.] 



SKA Woirni IXESS. [Snips.] 



SKIJACIC ACID. [SEBACIC GROUP.] 



SEBACIC GROUP. A small class of chemical compounds belong- 

 ing to the pelargonic series in Gerhardt's arrangement. The principal 

 member is .! .u/ic acid. 



Stbadc uriil (C,,,H in O ,2HO) or pyroleie acid is always obtained 

 when oleic acid or an oil containing olcic acid is distilled. " It is most 

 advantageously prepared by the action of a hot and very strong solu- 

 tion of caustic potash upon castor oil. The ricinolic acid of the castor 

 oil is thus split up into sebacic acid, caprylic alcohol, and free h\ 

 Sebacic acid is soluble in hot water, and crystallises out from a boiling 

 solution of the sebate of potash, produced as just indicated, on the 

 addition of hydrochloric acid. It forms white lamellar or acicular 

 crystals, of the appearance of benzole acid ; is very soluble in alcohol, 

 ether, or oils; reddens litmus paper; melts when heated to 260 

 Fahr., and at a higher temperature sublimes. Nitric acid converts it 

 into succinic acid. 



Sebacic acid is bibasic, forming neutral sclates of the formula 2MO, 

 C M H 10 ; and acid salts containing MO,HO,C, H ie O e . The alkaline 

 salts are nearly all crystalline and soluble in water; from them the 

 other sebates are prepared by double decomposition. Sebate of mc//i>/l 

 or methyl sebacic ether contains C 20 H ]0 (C, ! H, 1 ) 2 8 ; by contact with 

 ammonia it gradually yields scbamide (Cj^^N.O.) in crystalline 

 grains, the mother liquor containing selamic acid (C., H ie N0 ). 



Ipomic acid seems to be identical with sebacic acid. Jalap (ipomea 

 purga) resin yields rhodeoretic acid when acted on by bases, and 

 rhodeoretic acid furnishes ipomic acid on being oxidised by nitric acid. 

 The fusing point of ipomic acid is 40 degrees below that of sebacic acid, 

 but in every other respect it resembles the latter body. 



SEBAM1C ACID. [SEBACIC GROUP.] 



SEBAMIDE. [SEBACIC GROUP.] 



SEBAT (in Hebrew, 132$), is the fifth month of the civil year of 



the Jews. The name is mentioned in the 7th verse of the 1st chapter 

 of Zechariah, where it is called the eleventh month, reckoning from the 

 vernal equinox, at which season the Jews anciently began their year. 

 It is called Sabat in the Apocrypha, at 1 Mace. xvi. 14. The name is 

 found at Palmyra written as in Hebrew, and at Balbek it was written 

 2o,6a5. Sebat has thirty days ; its place in the year varies from 

 January to February, and in 1860 it began on the 25th of January 

 and ended on the 23rd of February. In 1861 it began on the 12th of 

 January and ended on the 10th of February. A fast is mentioned in 

 some calendars on the 4th day of Sebat, for the wickedness of Israel 

 after the death of Joshua, and another on the 23rd day, in memory 

 of the war between the tribe of Benjamin and the rest of the nation, 

 related in the 20th chapter of Judges ; but these fasts are observed 

 very partially, if at all. 



SEBIN. (C M W K O a ). The sebate of glycerin. It is neutral and 

 crystalline, and is transformed by oxide of lead into sebacic acid and 

 glycerin. 



ALE CORNUTUM. [EnooT.] 



SECANT, a line which cuts another; also a term in THIGOXOMETRY. 



SECEDERS. The origin and history of the Seceders from the 

 Established Church of Scotland will be found briefly stated in the 

 article UNITED PRESBYTERIAN Curncii, that being the name adopted 

 by the religious fellowship which includes the greater number of 

 Seceders. The Synod of United Original Seceders, the only body which 

 retains the name Seceders in its official designation, professes the same 

 doctrine and discipline as the United Presbyterian Church, but main- 

 tains the principle of a national church, and also that of national 

 religious vowing or covenanting. The Original Seceders number about 

 : negations, forming 4 presbyteries. Since the disruption in 

 1843 [FREE CHURCH OF SCOTLAND], many of those known as Original 

 Secedem and Associate or Old Light Burghers, have joined the Freo 

 Church, on the ground of its being, in their judgment, the truu 

 Xation.il Reformed Church of Scotland. 



SKCOXD, the sixtieth part of a minute, whether of time or of 

 angular measure. [ANGLE ; TIME.] For the derivation of this word, 



I-PI.E. 



sl'.i 'OND, an interval in music, a discord, the ratio of which is 9 : 8. 

 Of seconds there are three kinds : the minor second, or semitone, as 

 E i- ; the major second, c v ; and the extreme sharp second, c v ; 

 Ex.: 



SECOND-SIGHT, a power believed to be possessed by some persons 

 in the highlands and Islands of Scotland, of foreseeing future events, 

 especially of a disastrous kind, by means of a spectral exhibition of the 

 persons whom these events respect, accompanied with such emblems 

 as denote their fate. 



Jamieson says, " Whether this power was communicated to the 

 inhabitants of the highlands and islands of Scotland by the northern 

 nations, who so long had possession of the latter, I shall not pretend 

 to determine ; but traces of the same wonderful faculty may be found 

 among the Scandinavians. Is), ramikyyn denotes one who is endowed 

 with the power of seeing spirits : ' qui tali visu prater naturam prso- 

 ditus est, ut spiritus et dtcmones videat, opaca ctiam viu penetret." 

 Verel. Ind. The designation is formed from ramm-ur, viribus pollens, 

 nncl 'I i/nn, vidcns; g. r. powerful in vision." 



Dr. Johnson, in his journey to the Western Islands of Scotland, 

 carefully examined the questions of the second-sight ; but neither ho 

 nor Dr. Beattie could find sufficient evidence of it reality. 



In .Sir Jcihn Sinclair's 'Statistical Account of Scotland," vol. iii., 

 8vo., Edinb.. 17!^, the minister of Applecross, in the county of Ross, 

 speaking of his parishioners, says, " with them the belief of the second- 

 sight is general." 



In MacCulloch's 'Western Islands of Scotland,' 8vo., Lond., 1S19, 

 vol. ii., the author says, " To have circumnavigated the Western Mea 

 without even mentioning the second-sight would be unpardonable. 

 No inhabitant of St. Kilda pretended to have been forewarned of our 

 arrival. In fact it has undergone the fate of witchcraft ; ceasing to be 

 believed, it has ceased to exist." 



In the Erse the second-sight is called T 



SECONDARY, a name given to any circle on the sphere with 



