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important was a predisposition due to impaired strength from 

 any cause whatever. Too little exposure to fresh air inducing 

 depressed vitality might thus figure as a cause. His essay on 

 this topic with some alterations would make a good sanitary 

 tract, even after the lapse of more than a century. 



It was his constant habit to try to see all things little and 

 great just as they are, and when he spoke of them to give a 

 truthful report. When the time came for him to resort to 

 spectacles to correct old sight, he found that the glass which 

 served for society would not answer for reading. Naught that 

 interested him was he content to look upon as if in a fog. But 

 many things must be outlined dimly unless he carried two 

 pairs of spectacles and changed them as the occasion demanded. 

 To obviate this difficulty, he invented what is known as the 

 bifocal or Franklin lens, the upper half of which was adjusted 

 to distant objects and the lower for near view, as in reading. 

 By changing the direction of vision through this one pair of 

 glasses an elderly artist can see equally well the landscape one 

 moment and his canvas the next. Franklin asserted that he 

 understood French better by their help as they enabled him, 

 while at table to see distinctly what he had on his plate and 

 at the same, time to note the expressive facial movements of 

 persons who sat opposite. In the hundred years no change 

 was made from the original form until recently. Now, instead 

 of dividing the lens in equal halves by a horizontal line, two 

 perfectly centred lenses of different sizes are cemented together. 

 The larger, having two-thirds the size of the entire glass, is 

 devoted to objects beyond arm's reach, and the smaller at the 

 bottom suffices for reading. This invention must be considered 

 as something better than a convenience ; it takes rank with 

 devices for maintaining health. When the imperfect eye 

 makes frequent effort to see things without properly adjusted 



