298 - PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



ing. The child was then about 5 years old, and exceedingly tractable and 

 sensible, which enabled Dr. D. to make the following observations with great 

 accuracy and frequent repetition. 



1 . He viewed every object which was presented to him with only one eye at 

 a time. 2. If the object was presented on his right side, he viewed it with his 

 left eye ; and if it was presented on his left side, he viewed it with his right eye. 

 3. He turned the pupil of that eye, which was on the same side with the object, 

 in such a direction, that the image of the object might fall on that part of the 

 bottom of the eye where the optic nerve enters it. 4. When an object was held 

 directly before him, he turned his head a little to one side, and observed it with 

 only one eye, viz. with that most distant from the object, turning away the other 

 in the manner above described ; and when he became tired with observing it 

 with that eye, he turned his head the contrary way, and observed it with the 

 other eye alone, with equal facility ; but never turned the axes of both eyes on 

 it at the same time. 5. He saw letters, which were written on bits of paper, 

 so as to name them with equal ease, and at equal distances, with one eye as with 

 the other. 6. There was no perceptible difference in the diameters of the 

 irises, nor in the contractibility of them, after having covered his eyes from the 

 light. These observations were carefully made by writing single letters on shreds 

 of paper, and laying wagers with the child that he could not read them when 

 they were presented at certain distances and directions. 



From these circumstances it appeared, that there was no defect in either eye, 

 which is the common cause of squinting, so well observed by M. Buftbn and 

 Dr. Reid ; and hence, that the disease was simply a depraved habit of moving 

 his eyes, and might probably be occasioned by the form of a cap or head-dress, 

 which might have been too prominent on the sides of his face, like bluffs used 

 on coach-horses ; and might thence, in early infancy, have made it more con- 

 venient for the child to view objects placed obliquely with the opposite eye, till 

 by habit the musculi adductores were become stronger, and more ready for 

 motion than their antagonists. 



A paper gnomon was made, and fixed to a cap ; and when this artificial nose 

 was placed over his real nose, so as to project an inch between his eyes, the 

 child, rather than turn his head so far to look at oblique objects, immediately 

 began to view them with that eye which was next to them. But the death of 

 Dr. Sandford, which happened soon after, occasioned the removal of his family ; 

 and the grief and cares of Mrs. Sandford prevented this, and the other methods 

 proposed, from being put in execution. 



In Feb. 1777, Dr. D. had again an opportunity of seeing master Sandford, 

 and observed all the circumstances of his mode of vision to be exactly as they 

 were 6 years before, except that they seemed established by longer habit ; so 



