and distant Sight of different Persons. '47 



trying with different glasses, he discovered that, by looking 

 through a double concave glass of the sixth number, ( which 

 is ground to a radius of eight inches on one side and eleven 

 inches on the other,) he was enabled to see distant objects . 

 distinctly. He has continued to use glasses of this description 

 for the purpose of seeing distant objects from that time to the 

 present ; but is obliged to remove them whenever he reads, 

 and still to employ the first number of a convex glass. — In this 

 instance, a presbyopic was changed to a myopic sight, without 

 any known efficient circumstance to produce it. — In the two 

 following cases, a similar change took place ; and in them it 

 was attributable to known causes. A woman, about fifty years 

 of age, of a full habit^ who for several years had been obliged 

 to make use of convex glasses, in order to read a small print, 

 was seized with a dimness in the sight of the right eye, ac- 

 companied with a small degree of inflammation. The sight of 

 the left eye having been long imperfect, this affection of the 

 right eye occasioned a great depression of spirits. Recourse 

 was necessarily had to copious evacuations, by means of 

 which the inflammation and dimness of sight were soon 

 removed ; but afterwards the patient was much alarmed on 

 finding that the spectacles she had been accustomed to wear, 

 instead of affording their usual assistance, confused her sight. 

 Upon this discovery, she was induced to look through her 

 husband's glasses, which, in consequence of his being near 

 sighted, were double concaves of the fifth number, and ground 

 to a radius of eleven inches on each side. These did not as«- 

 sist her in looking at near objects, but by their aid she saw 

 much more distinctly those that were distant; and, on attempt- 

 ing to read, nothing more was now necessary, than to bring 



