Greater Light drowns lesser light ; Sounds are sweeter at night

From The Merchant of Venice  5.1.89-101

Portia:  That light we see is burning in my hall:
            How far that little candle throws his beams!
             So shines a good deed in a naught world.
Nerissa: When the moon shone we did not see the candle.
Portia:    So doth the greater glory dim the less,-
             A substitute shines brightly as a king
             Until a king be by, and then his state
             Empties itself, as doth an inland brook
             Into the main waters: - music - hark!
Nerissa: It is your music (madam) of the house.
Portia:   Nothing is good (I see) without respect, -
             Methinks it sounds much sweeter than by day.
Nerissa: Silence bestows that virtue on it madam.

As J.M. Robertson commented in his The Baconian Heresy p. 435: "Shakespeare frequently introduces the idea of reactions and relations between the greater and the less, the greater 'hiding' or overshadowing or obscuring or absorbing the other, as in the case of lights, griefs, maladies, or sea or river". One illustration of this is afforded by L1.92-97 above. Bacon makes the same two points in his A Brief Discourse touching the Happy Union of the Kingdom of England and Scotland (1603):

"The second condition [of perfect mixture] is that the greater draws the less. So we see when two lights meet, the greater doth darken and drown the less. And when a smaller river runs into a greater, it loseth both the name and stream."

The second of these two observations was commonplace; the first somewhat less so. What is striking about this parallel is that Shake-Speare and Bacon use the same two "the less in the greater" phenomena in conjunction and in the same order. J.M Robertson was a little troubled by this, and to explain it he suggested (p. 435) that both authors may have copied an earlier source, or that Bacon may have watched or read the play. But there is no evidence of an earlier source. And would Bacon, years later when he made his comment of general application, have remembered and borrowed from a particular application of it in the play? Besides, Bacon is likely to have formed his views on such matters long before the play was published in 1600.

Now look at L1.100-1 and compare Bacon's Natural History
"Sounds are meliorated by the intension [intensification] of the sense, where the common sense is collected most to the particular sense of hearing, and the sight suspended; and therefore sounds are sweeter as well as greater in the night than in the day."

That sounds seem greater at night was of course a commonplace, and is expressed by Shake-Speare, together with the reason Bacon gives for it, in A Midsummer Night's Dream 3.2.177-8:

Dark night, that from the eye his function takes
The ear more quick of apprehension makes,
Wherein it doth impair the seeing sense,
It pays the hearing double recompense.

Compare to Bacon's "The apprehension of the eye is quicker than that of the ear"
--Natural History

However, the notion that sounds seem sweeter at night was surely not a commonplace; yet is is voiced by both authors. And they probably agree as to the reason for it. Just as Bacon in his Natural History says: "As for the night, it is true also that the general silence helpeth". He is speaking of sounds seeming greater at night, but he probably regarded the general silence as one reason for their seeming sweeter as well. It was chronologically impossible for Shake-Speare to have borrowed from Bacon, though Bacon could have borrowed from the play.