Chap. 4. PHILOSOPHY. 381

whence the rays actually proceed. But converging rays willbe made either to converge less, or even to diverge.

6. I n these glasses rays, which proceed from any pointnear the axis, will be affected as it were in the fame man-ner, as if they proceeded from the very axis it self, and fiich asconverge toward a point at a small distance from the axis willsuffer much the same effects from the glals,as isthey converged tosome point in the very axis. By this means any luminous bodyexposed to a convex glass may have an image formed uponany white body held beyond the glass. This may be ea-sily tried with a common Ipectacle-glass. For if such a glassbe held between a candle and a piece of white paper, if thedistances of the candle, glass, and paper be properly adjusted,the image of the candle will appear very distinctly upon thepaper , but be seen inverted ; the reason whereof is this ..Let AB (in fig. 1 yi) be the glass, CD an object placedcross the axis of the glass. Let the rays of light, which isssue from the point E, where the axis os the glass crosses the ob-ject, be so refracted by the glass, as to meet again about thepoint F. The rays, which diverge from the point C of theobject, shall meet again almost at the same distance fromthe glass, but on the other fide of the axis, as at G j for therays at the glass cross the axis. In like manner the rays,which proceed from the point D, will meet about H on theother side of the axis. None of these rays, neither those,which proceed from the point E in the axis, nor those whichissue from C or D, will meet again exactly in one point; butyet in one place,, as is. here supposed at F, G, and H, they

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