Dr. G. J. Stoney on Microscopic Vision, 427 



Some of this detail may be in excess of any detail shown 

 in Image B, but, unfortunately, an addition of this kind 

 does not represent anything on the microscopic object 

 (Part I., Proposition 3, p. 345) . 



Image C and Object C, like Image B and Object B, 

 are of the same size as the microscopic object. 



D. Image D 7 the focal image formed by the objective, 

 which lies near the top of the tube of the microscope, is 

 an enlargement with distortion of Image C. To it 

 corresponds Object D, viz. that object which the focal 

 image if seen would appear to be. 



E. Image E, the visual image, is that virtual image 

 which the eye-piece forms, when it is applied as a mag- 

 nifying-glass to the focal image. It is an enlargement 

 and slight distortion of the focal image. It is, therefore, 

 an enlargement with a somewhat different distortion of 

 Image C. To it corresponds Object E, the visual object, 

 that object which the observer thinks he sees. 



F. Finally Image F is the image actually produced 

 on the retina of the observer. 



The state in which the light has been admitted to the object 

 affects images B, C, D, E and the corresponding objects, and 

 therefore affects Image F. We have now to advance in suc- 

 cession through these images, beginning with the ideal image 

 and ending with the image which is actually formed within 

 the eye of the observer. 



23. Transition from A to B. — Image A, an ideal image of 

 the microscopical object, could only be formed by light of 

 infinitesimal wave-length supplied in a theoretically perfect 

 manner. This light, and this light alone, could form an 

 image reproducing every detail. By such wave-lengths as 

 can be used with the microscope — i. e. when we pass from 

 Image A formed by imaginary light of infinitesimal wave- 

 length to Image B formed out of real light — the greater part 

 of the events that happen in the object are shut out from our 

 view by being massed together. In fact, when we come to a 

 numerical example we shall find that a whole squadron of 

 them, indeed an entire army, occupies that space upon the 

 object which corresponds to the minutest speck which such 

 light will show. 



Image B, the standard image, as appears from § 8, p. 338, 

 is formed by the flowing in upon it of beams of uniform plane 

 waves ; and in consequence it may, under Theorem 2, be re- 

 garded as formed of luminous rulings interlacing and inter- 

 fering with one another : each luminous ruling being formed 



