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The School of Arts; Or, an Introduction to Useful Knowledge
The School of Arts Or an Introduction to Useful Knowledge Author:John Imison General Books publication date: 2009 Original publication date: 1796 Original Publisher: Printed for J. Murray and S. Highley Notes: This is a black and white OCR reprint of the original. It has no illustrations and there may be typos or missing text. When you buy the General Books edition of this book you get free trial access to Million-Bo... more »oks.com where you can select from more than a million books for free. Excerpt: OPTICS. AS the fenfe of feeing is the nobleft belonging to an animal; without which he would live in perpetual darknefs, . unable to perform the neceflary exercifesof life; and fince all that has been demonftrated of glafles, and will hereafter be demonftrated of all optical machines, tend only to this fingle end, to help and improve the fenfe of feeing; and fince the eye is the organ or in- ftrument by which vifion is performed, -- it is by nature an optical inftrument, and the foundation of all others; arid therefore it cannot be amifs to give a fhort defcrip- tion thereof. Plate X11. A B C E is the eye, its figure fpherical; by reafon of Fig. i. which, it is eafily moved any way in its focket. The fore-part at A is more convex than the reft. It is contained in three membranes; theoutermoft is HieScIerotica; the fecond the Tunica Choroidesi the fore-part is called the fris, which confifts of many fibres, like fo many radii. The third, or innermoft, is called the Retina ; which is nothing but the optic nerve, fpread ver the bottom of the eye. In thefe are contained the three humours of the eye; the iirft is H A I, called the Aqueous humour, which is a thin'95 . 8t« less