Page:Batman upon Bartolome.djvu/73

 ''In pri. cap. Perſpectiue,'' the Philoſopher ſaith, that in thrée manners the ſight is made. One manner by ſtraight lynes, vpon the which, the lykeneſſe of thing that is ſéene, commeth to the ſight. Another manner vpon lynes rebounded againe: when the lykeneſſe of a thing commeth there from to a ſhewer, and is bend, and reboundeth from the ſhewer to the ſight. The thirde manner is by lynes, the which though they be not bent and rebounded, but ſtretched betwéene the thing that is ſéene and the ſight: yet they paſſe not alwaye foorthright, but other while they ſwarue ſome whether aſide from the ſtraight waye. And that is when diuers manner ſpaces of diuers cléereneſſe and thickneſſe, be put betwéen the ſight and the thing that is ſéene: and ſometime the ſpaces be of diuers kindes, as when one is thicker, another thinner. And ſometime there commeth a meane of another kinde, but the beame or bright likenes is broke, but if it come vpon a line that falleth ſtraight, & Perpendiculariter vppon the ſame middle ſecond occurring. And I cal a line to fall Perpendiculariter vpon a plaine thing, Ad angulos rectos, that is ſtraight and a croſſe wiſe: and vpon a round thing, if it fall into the middle thereof.

To the ſight, for to ſpeake in the firſt manner, néed nine things principally, as they be reherſed ther. The firſt is firmneſſe or good diſpoſition of the organe or inſtrument of ſight. The ſeconde is a thing that may be ſéene ſet afore ſight: for in  manner the ſight ſéeth nothing. but if the ſame thing, from the partes, wherof commeth likenes vpon ſtraight lynes, that fall into the middle of the eye. All which lynes drawen from all the parts of the thing that is ſéene, make one ſtéeple, the poynt whereof is in the blacke of the eye, and the broad end in the thing that is ſéene as appeareth in this figure.

A and B be the Axiltrées, when the ſéeing directlye beholdeth the poynt, C, when it beholdeth point D. Then theſe two B C procéeding from the eyes, be called axiltrees, for they procéede immediatelye from the eyes, by meane to the thing ſeene. The third is diſtance proportional. The fourth D C is a certaine ſtede or place, not too farrre from the lyne of the ſight. For though a thing be right before the eye, if it be too far ther from, it is not diſtinctly known. Axis viſualis is the cléere beame or line, the whichlis vnderſtood to be deduct from the middle of the ſight, to the poynt of the thing ſéene directly to the oppoſite, in the mids of the ſight, as appereth in this figure A B. The fift is ſadnes or thickneſſe of the thing that is ſéene. For if it be all cleare and without thickneſſe, as the aire is, then that is not ſéene, as ſaith the Author of the ſcience Perſpectiue, that is, the ſcience of the ſight. The ſixt, is due greatneſſe of the thing is ſéene. For a thing may be ſo lyttle, it cannot be ſéene in no ſpace: for there is no ſight but by appearance ſhapen top wiſe, that commeth to the eye,  which if it be very little, it ſhal occupie a very ſmal part of the ſight, & the ſight may not ſée, but when a part of the vttermoſt thereof is changed to the likenes of the thing that is ſéene. The vii. is clearneſſe of ſpace, that is betwéene the eye & the thing that is ſéene: for if the ſpace be thick, it letteth the likeneſſe of that thing, that it may not come lightly & in due manner to the black of the eye. The viii. is light: for the viſible lykeneſſe of the thing, can not chaunge the ſight without lyght. The ninth is time, for the ſight muſt haue time, as it is proued in Perſpectiue: for though a thing come ſodainly before the ſight: it is not knowne readily and diſtinctly without ſome aduiſement had, the which needeth time and leaſure. And therefore it needeth alſo that the ſoule take heede, as it is ſayde before. Alſo the Philoſopher ſayeth, That not onelye the lykeneſſe of the thing ſeene commeth to the ſight after a ſteeple wiſe, but alſo the lykeneſſe of the ſight, ſtretcheth to the thing that is ſpread, vppon ſuch a ſteeple in the ſame place. In lib. 19. De Animalibus, Ariſtotle ſaith, That ſeeing is nought els, but that the ſight paſſeth out to the thing that is ſeene.