362 Mr. airy, on an EYE AFFECTED WITH A MAL-FORMATION. 



On examining the slightly discordant observations, I am inclined to think that a distance somewhat 

 less than 4'7 is the true) one, and this would increase the measure of astigmatism above 0-100, and 

 would make it approach more nearly to the ancient value. It seems therefore that whilejthe short- 

 sightedness of the eye has materially diminished, the fault which produces the astigmatism has 

 undergone very little or no alteration. 



Upon examining the right eye in the same manner, I find no perceptible fault. The image of 

 a fine hole is a luminous point very sharply defined. The distance of accurate definition is as nearly 

 as possible 4'7 inches, the same as the nearest distance at which the left eye forms a well defined line 

 for the image of a point. It would seem therefore that the normal formation of the two eyes is the 

 same, and that the abnormal alteration in the left eye is of the nature of a refraction through a dense 

 medium cylindrically concave, or through a rare medium cylindrically convex, superadded to the 

 normal refraction. 



G. B. AIRY. 



Royal Observatory, Greenwich, 

 January 14, 1846. 



