Sentence:  ... I should have been apt to think, that the young gentlewomen and Mr. Lovelace were of longer acquaintance than yesterday. For he, by stealth, as it were, cast glances sometimes at them, which they returned; and, on my <WSD>ocular</WSD> notice, their eyes fell, as I may say, under my eye, as if they could not stand its examination. 
Meaning of the word marked with <WSD> tags:  Seen by, or seeing with, the eye; visual.