94 EXPERIMENTS, &c. 



ARTICLE III. 



On the Connexion between the different refractive States 

 of the Eyes, and, the different Inclinations of the Optic 

 Axes to each other. 



I HAVE mentioned, in my Essay upon Single 

 Vision with Two Eyes *, that I had been con- 

 vinced, by experiments almost without number, 

 that every different degree of the mutual in- 

 clination of the optic axes, is attended by a dif- 

 ferent state of the refracting power of each eye. 

 The experiments I there alluded to were chiefly 

 of this sort. I placed a luminous point, most 

 commonly the reflected image of the flame of a 

 candle from the bulb of a small thermometer, 

 at such a distance, that when both my eyes 

 were accurately directed to it, its visible ap- 

 pearance to one of them was likewise that of a 

 point. Keeping then the axis of this eye fixed, 

 and making the other to cross it, sometimes 

 before and sometimes behind the luminous 

 point, I found that in both cases it appeared as 

 a surface to the eye, in the axis of which it was 



* Page 66. 



