on the Mechanism of the Eye. 87 
Fig. 25. Outline of the lens when relaxed ; from a compa- 
rison of M. Petit’s measures with the phenomena of my own 
eye, and on the supposition that it is found in a relaxed state 
after death. 
Fig. 2 6. Outline of the lens sufficiently changed to produce 
the shortest focal distance. 
Fig. 27. Apparatus for ascertaining the focal length of the 
lens in water. 
Plate VI. Fig. 28. Various forms of the image depicted by a 
cylindrical pencil of rays obliquely refracted by a spherical sur- 
face, when received on planes at distances progressively greater. 
Fig. 29. Image of a minute lucid object held very near to 
my eye. 
Fig. 30. The same appearance when the eye has been 
rubbed. 
Fig. 31 — 37. Different forms of the image of a lucid point 
at greater and greater distances ; the most perfect focus being 
like Fig. 33, but much smaller. 
Fig. 38. Image of a very remote point seen by my right eye. 
Fig. 39. Image of a remote point seen by my left eye ; being 
more obtuse at one end, probably from a less obliquity of the 
posterior surface of the crystalline lens. 
Fig. 40. Combination of two figures similar to the fifth 
variety of Fig. 28 ; to imitate Fig. 38. 
Fig. 41. Appearance of a distant lucid point when the eye is 
adapted to a very near object. 
Fig, 42, 44. Shadow of parallel wires in the image of a 
distant point, when the eye is relaxed. 
Fig. 43, 45. The same shadows rendered curved by a 
change in the figure of the crystalline lens. 
