S I G 



S I G 



SlGEUM Promantorium, a promontory of the Troade. It 

 M near to and north of the mouth of the river called Sca- 

 mander. Strabo calls it the port of the Achxans, bccaufe 

 the Greeks landed there in going to the fiege of Troy. In 

 the vicinity was a large lake, which was thought to com- 

 municate with the fea. This promontory is now called 

 Yeni-Hifari. 



SIGG, or SiKKE, in Geography, a river of Algiers, 

 which, united with the Habrah, forms the Muckda, or, as 

 it is firft called, Makerra. 



SIGGU, a town of Japan, in the ifland of Niphon ; 65 

 miles N.E. of Meaco. 



SIGHING, an effort of nature, by which the lungs are 

 put into greater motion, and more dilated, fo that the blood 

 palles more freely, and in greater quantity, to the left au- 

 ricle, and thence to the ventricle. Hence we learn, fays 

 Dr. Hales, how fighing increafes the force of the blood, 

 and conlequently proportionably chears and relieves nature, 

 when opprefled by its too flow motion, which is the cafe 

 of thoft who are dejefted and fad. Hales's Statiltical Efl. 

 vol. ii. p. 6. See Lungs, 



SIGHT, the exercife, or aft of the fenfe of feeing. See 

 Eyk. 



Our fight, the nobleft. and moft ufeful of all our fcnfes, 

 father Malebranche fhews, deceives us in abundance of in- 

 ftances ; nay, almoft in all : particularly with regard to the 

 magnitude and extent of things ; their figures, motions, &c. 

 Our eyes do not (hew any thing lefs than a mite : half a 

 mite is nothing, if we believe their report. A mite is only 

 a mathematical point, with regard to it ; and we cannot di- 

 vide it, without annihilating it. In effeft, our fight does 

 not reprefent extenfion, fuch as it is in itfelf ; but only the 

 relation and proportion it has to our body. Hence, as half 

 a mite has no relation to our bodies, and that it cannot 

 either preferve o^ deftroy us, our fight hides it entirely. 

 Were our eyes made like microfcopes, or were we ourfelves 

 as fmall as mites, we Ihould judge very differently of the 

 magnitude of bodies. 



It may be added, that our own eyes are really no other 

 than a kind of natural fpeftacles ; that their humours do 

 the fame office as the lens in fpeftacles ; and that, accord- 

 ing to the figure of the cryftalline, and its diftance from 

 the retina, objefts are feen very differently by us ; infomuch 

 that we are not fure, that there are any two perfons in the 

 world who fee them equally big. It is even very rare, that 

 the fame perfon fees the fame objeft equally big with both 

 eyes ; as both eyes are very feldom perfcftly alike : on the 

 contrary, we generally fee things bigger with the left than 

 the right eye ; of which wc have fome very good obferva- 

 tions in the journal of the learned at Rome, for the year 

 1669. See Vision. 



The Afta Leipficnfia give us an account of a man, who 

 received afmart Itroke on the pupil of one of his eyes from 

 the end of a fiddle-ltring, which broke while he was tuning 

 the inilrument, and chanced to fly that way. Some cooling 

 things were applied to the eye, and a bandage ufcd to Ihade 

 it from the light ; but at midnight the patient, chancing to 

 wake in the dark, found that he could fee with that eye, 

 though not with the other : this continued a long time, and 

 on trial he found that he could read a fmall print at midnight 

 with this eye, but could fcarcely dillinguilh any thing with 

 it in a bright and clear day. 



We have, in the fame coUoftions, an account of a man, 

 who, after the cure of a confirmed pox, faw every objcft 

 double for a long time. Aft. Leipf. 1690. 



It is a very common, and a very jull obfcrvation, that 

 Vol. XXXII. 



children do not fee any thing clearly when new-bom ; and 

 if their eyes be then examined, they are found to want tiiat 

 brilliancy which they afterwards acquire ; and finally, when 

 any objeft is prefented to their view, they at firlt turn their 

 eyes about in (iich a manner, that it is evident they either do 

 not fee at all, or at be ft but very imperfeftly and obfcurely. 



This imperfeftion may either be owing to a fault in fome 

 one of the humours, or in their capfules ; or, finally, in the 

 retina, or complexly in them all together. It is impoffible 

 to difcover whether there be any imperfeftion in the retina 

 in this ftate of life, that membrane being ever, in new-born 

 infants, tender and foft like a jelly : if it be m any of the 

 other parts that the imperfeftion lies, it muft be either in 

 their nature or extent. M. Petit, of the Academy of 

 Sciences at Paris, determining to enquire thoroughly into 

 the caufe of this, was at the pains of difiefting the eyes of 

 feveral infants which had died foon after their birth, and in 

 three-fourths of them he found the vitreous, the cryftalline, 

 and the capfule, all greatly deficient in their tranfparence. 

 The uvea appeared alfo more opaque than in adults, and the 

 pupil over-large ; and that there was either none, or, at the 

 utmolt, very little of the aqueous humour ; and in thofe 

 eyes where the humours had not this opacity, they were all, 

 aa were alfo the membranes, of a reddilh colour ; and this 

 was obferved in fojtufes of fevei\ and nine months old. 



T)ie cornea in thefe eyes was alfo remarkably thick, 

 which is, in general, found to be the cafe in the eyes of all 

 foetufes. The thicknefs and opacity in thefe corneae gra- 

 dually dimiriifh in time, and that foon ; fo that the eyes of 

 children appear much brighter at two or three months old 

 than when new-born. The aqueous humour feems alfo, in 

 moft foetufes, to be wholly wanting ; and where it is found, 

 is ever greatly in an under proportion to the other humours. 



It therefore appears, that the dimnels and imperfeftion of 

 fight, in new-born infants, are owing to the over-thicknefs of 

 the cornea, and to the too fmall portion of the aqueous or 

 watery humour. It appears plainly alfo, from experience, 

 that the eye is not able, in infants, to bear the light, till the 

 pupil is greatly contrafted ; as is the cafe alfo, though in 

 a lefs degree, in adults ; and it is very probable, that the 

 extreme foftncfs of the retina in this ftate may make every 

 ray of light afleft it much more plainly than when grown 

 more firm. 



M. Petit having continued his examinations of the eyes 

 of infants, up to the age of five or (w weeks, found in all 

 his difteftions, that the cornea daily grew more and more 

 convex and glofTy ; and this may be rationally concluded to 

 be owing to the daily incrcale of the aqueous humour, which 

 muft, by that accretion, throw it out into a greater con- 

 vexity, and make it daily more and more thin and tranfparent. 

 The uvea alfo acquires a greater extenfion, and its fibres 

 become more moveable ; wlicnce the pupil acquires a power 

 of enlarging or contrafting itfelf, at the approach or ab- 

 fence of light, with much more eafe and rcadinefs tlian it 

 could before. The humours thus all become capable of 

 letting in a larger quantity of liglit ; the retina is at the 

 fame time every day gaining a new firmnefi, and the pupil 

 becomes capable of an cafy dilatation, or reftriftion, for the 

 letting in occafionally a greater or lefs number of rays, and 

 the rcfraftions are perfefted by the augmentation of the 

 aqueous humour. It is plain, therefore, that the clcarnefs 

 of vifion muft every day increafc. All this change comes 

 on in infants only by time ; and it may be judged of, as to 

 its ftate, l)y infpeftion, by the brilliancy and convexity of 

 the cornea, and by the manner of their turning their eyes 

 towards objefti let before them ; and this time is not cer- 

 4 R tain, 



