It has been of late the Opinion of very Learned men, that tho Both our Eyes be Open and turn’d towards an Object, yet ‘tis but One of them at a time that is effectually Imployed in giving us the Representation of it. Which Opinion, in this place where I am writing but Observations, it were not proper to Discuss; especially because what is suppos’d to be Observ’d, will not always Uniformly happen, but may much Vary in particular Persons, according to their several Customs, and the Constitution of their Eyes. For I have, by an Experiment purposely made, several times found, that my Two Eyes Together see an Object in another Situation, than Either of them Apart would do. On the other side; I met with a Person, who told me he had a Cataract in his Eye for two Years, without discerning that he had any such Impediment in either of his Eyes; and when I ask’d him, how he knew that, he answer’d me, that others had taken notice of a white Filme that cross’d his Eye, so long before he himself did. But not knowing what a Cataract was, and not finding him to complain of it at all himself, the Thing remain’d unheeded, till the Patient, having one day occasion to Rub his Sound Eye, whilst the Lid cover’d it, was sadly Surpriz’d to find himself altogether in the Dark; and then resorting to an Oculist, was assur’d it was a Cataract, which, a while before I met with him, had been Couch’d. But notwithstanding this Relation, what I had try’d about the Using of Both Eyes, made me ask of a very Ingenious Person, that by an Accident had some months before one of his Eyes struck out, whether he did not observe, that upon the being confin’d to the use of One Eye he was apt to mistake the Situation and Distances of things. To which he answer’d me, that haveing frequently occasion to pour Distill’d Waters and other Liquors out of one Vial into an other, after this Accident he often Spilt his Liquors, by pouring quite Besides the necks of the Vials he thought he was pouring them directly Into. Afterwards inquiring of a Gentleman that was a Goodfellow, and had by a Wound a while before lost the use of One of his Eyes; he confess’d to me, that divers times pouring the Wine out of one Vessel into another, he would miss the Orifice of the Bottle or Glass that should receive it, and expose himself to the merriment of the Company. A yet more considerable Instance of Such Mistakes, I afterwards had from a Noble Person, who having in a Fight, where he play’d the Hero, had one of his Eyes strangely Shot out, by a Musquet-Bullet that came out at his Mouth; answer’d me, that not only he could not well Pour Drink out of one Vessel into another, but had Broken many Glasses, by letting them fall out of His Hand, when he thought he had put them into Anothers, or set them down upon a Table. And he added, that this aptnesse to misjudge of Distances and Situations continued with him, tho’ not in the same Degree, for little less than Two Years. But on this occasion I shall take notice that, I have often imployed a Dextrous Artificer, whose Right Eye (for in his Left there is nothing more remarkable) is constantly drawn so much a side towards the greater Angle of the Eye, that the Edge of the Pupil does almost touch it and one would think it scarce possible, but that he should see the Object double with two Eyes that seem so very differingly turn’d; and yet he answer’d me, that he does not see at all, nor that he finds any Inconvenience, save the Deformity of this Unusual Situation of his Right Eye, which hinders him not from Reading as freely as other Men. This Accident happend to him by an unwary Mistake of Sublimate for another thing; after which, it seems one of the Muscles that mov’d the Eye, remain’d Contracted. But this having happen’d to him, as I found by Inquiry, ever since he was two Years of Age; he could not remember whether he had seen Objects Double, before he was accustom’d to judge of them by the help of his other Senses, and the Information of Others.
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