﻿134 



Prof. J. LeConte on some Phenomena 



If, now, while viewing the image in the last experiment, we 

 repeat upon it the same experiment, i. e. if by increasing the 

 convergence of the optic axes we bring again the two contiguous 

 figures into coincidence, a new image is formed between the last 

 and the eye, and is seen in still smaller miniature. In this case 

 the position of the optic axes is such that the eyes crossing are 

 directed, not toward contiguous figures of the real object, but to 

 figures separated by an intervening one. Thus in the figure 

 (fig. 2) a and c will be combined and seen at a 11 , d and b at d", 

 and b and e at e". 



Upon this second image the same experiment may be repeated 

 so as to make a third image still smaller and nearer the eye at 

 d w , e'", and from the 

 third even a fourth and 

 still smaller image may 

 be formed at e"". The 

 positions of these succes- 

 sive planes are indicated 

 by the dotted lines ; but 

 in this figure the posi- 

 tion of the axes is only 

 adapted to vision on 

 plane No. 2. For the 

 higher planes, the optic 

 axes must converge still 

 more. For the fourth 

 plane I e and lid will 

 represent the visual 

 lines. Standing erect 



and looking down upon the regularly checkered carpet on the 

 floor of my room, the figures of which are 4 J inches from centre 

 to centre, I can with the greatest ease bring out successively 

 four distinct images one above the other, the nearest being but 

 seven inches from my eyes, and the figures (which are 2 inches 

 in diameter in the carpet) reduced to about \ inch in diameter. 

 If while looking at the image on the fourth plane the conver- 

 gence of the optic axes be suddenly relaxed, the image drops and 

 may be caught on No. 3. Again, by relaxing the convergence 

 it may be dropped and caught on successive planes until it falls 

 to its natural position. 



I have made similar experiments on a great variety of patterns 

 of wall-papering, oil-cloths, calicoes, &c. with the same results. 

 Of a regularly checked oil-cloth in my hall, the lozenge-shaped 

 figures of which are 10" 2 inches across, I make successively 

 three perfectly distinct images, the nearest being but 4^ inches 

 from the eyes. 



