Dr. J. Reade ok a hex 1 %wy of ']'< I, scopes. 2."> 



fact, the incontrovertible fact, that this focal image when in- 

 tercepted by the card was nearly two inches in breadth, ami 

 yet the pupil through which they were to pass was not l-4th 

 of an inch, nor the eye-hole of the telescope l-20th of an inch. 

 And, as already mentioned, if q E/? measured the magnifying 

 power, the further the eye was removed from the eye-glass 

 the larger the object should appear: that the reverse is* the fact 

 must be known to every experimenter; indeed at a little di- 

 stance the extreme rays coming from Q and P and crossing 

 at L and then diverging, would not only clear the pupil itself, 

 but the very ears of the spectator ; consequently to argue that 

 We see the object by means of these rays, is absurd. 



The fourth objection I have to bring forward is, that focal 

 images are always painted immediately in the axis of the lens, 

 and no where else. Therefore, if these inverted images were 

 the cause of vision, the pupil of the observer's eye should be 

 always placed in the axis of the lens, and no where else. I low- 

 ever, direct experiment informs us that we can see through a 

 refracting telescope, when the eye is removed considerably to 

 the right or left of the axis. Indeed I have been enabled to 

 see the inverted image of an object painted on the bull's eye, 

 when my pupil was at right angles with the axis, where it 

 was impossible that any of these rays could enter the eye. 



Having thus shown, I hope to the satisfaction of my readers, 

 that this mathematical theory of the Galilean telescope is fal- 

 lacious, I shall now endeavour to substitute a more rational 

 theory, and one founded on direct experiment. I must refer 

 to my former paper on Vision for those experiments which 

 prove that rays diverge in passing through a convex lens, and 

 converge in passing through a concave one. I have also, 

 shown in a former paper that rays never form focal images by 

 crossing, which forms another strong objection. I laving pro- 

 cured a convexo-convex lens, whose focus was about two feet, 

 and a concavo-concave lens for an eye-glass, Number 1 7, I 

 covered half the concave lens or eye-glass with a piece of 

 white paper. I now held these two lenses opposite a lighted 

 candle so as to form a telescope without the tube, and on re- 

 moving the object-glass to the proper distance from the eve- 

 glass, I perceived the candle erect and considerably magnified 

 in all its dimensions; and I also perceived an inverted image 

 of the candle, painted on the paper of the eye-glass. Here 

 I again assert, that it would be metaphysically absurd to say 

 that rays coming from this inverted image produced both the 

 sensation of an erect and at the same time of an inverted 

 image. 



Vol. §3. No. 309. Jan. 1821. D The 



