such an anomaly that St. Augustine (Confessions  5, 3) 
     finds Ambrose’s habit a very remarkable thing: “But when 
     he was reading his eye glided over the pages and his heart 
     searched out the sense, but his voice and tongue were at 
     rest.” Visitors came to watch this prodigy, and Augustine 
     conjectures explanations:

          ‘Perchance he dreaded lest if the author he read 
     should deliver anything obscurely, some attentive or 
     perplexed hearer should desire him to expound it, or to 
     discuss some of the harder questions; so that his time 
     being thus spent, he could not turn over so many 
     volumes as he desired; although the preserving of his 
     voice (which a very little speaking would weaken) might 
     be the truer reason for his reading to himself. But with 
     what intent soever he did it, certainly in such a man it