on Muscular Motion. 
*5 
yards, through the hole in the brass plate, and afterwards to 
look at the edge of the small hole itself, which was only 6 
inches from the eye. In doing this several times, the curved 
lines were seen to separate from each other ; and the micro- 
scope required being withdrawn from the object whenever the 
person's eye was adjusted to the near distance ; but the very 
reverse took place when it was fixed on the distant one. 
In making these experiments, the least motion of the head 
carried the cornea out of the field of the microscope ; it was 
therefore necessary that the two objects should be exactly in 
the same line respecting the eye, and that the person should 
remain silent. When he complied with any request which 
had been made, he signified by touching the knee of the ob- 
server with his hand, that he had done so. This experiment 
was made upon the eyes of all present, and the same appear- 
ances were uniformly observed ; and after several trials we be- 
came so familiar with the appearances, that the observer only 
required information of the adjustment having been changed, to 
enable him to tell which of the objects the eye was fixed upon. 
August the 1 st, about four o'clock, these experiments were 
repeated, and after several attempts were made, without suc- 
cess, to explain the cause of the curved lines, we found it neces- 
sary to shade a part of the window, to take off the glare of 
light which fatigued the eye, and rendered it unsteady ; this 
made the curved lines less distinct ; and when the whole win- 
dow was shaded they disappeared altogether, leaving a very 
distinct view of the whole thickness of the cornea, with a well 
defined line formed by its anterior projecting surface. This 
discovery proved the curved lines to be reflections from the 
sides of the window upon the cornea ; but as it was not made 
