Here it is, from Chapter 40:
(Nicholas is utterly in love with a girl he's had only a glimpse of. For a long time now, he's been surviving only on the 'mental picture' of her that he's conjured up. He's trying everything he can within his (rather limited) means to get to know more of her, and has not been seeing too much success. After a particularly bright ray of hope dimmed, Dickens makes this comment.)
What a crack!
Mystery and disappointment are not absolutely indispensable to the
growth of love, but they are, very often, its powerful auxiliaries.
'Out of sight, out of mind,' is well enough as a proverb applicable
to cases of friendship, though absence is not always necessary to
hollowness of heart, even between friends, and truth and honesty,
like precious stones, are perhaps most easily imitated at a
distance, when the counterfeits often pass for real. Love, however,
is very materially assisted by a warm and active imagination: which
has a long memory, and will thrive, for a considerable time, on very
slight and sparing food. Thus it is, that it often attains its most
luxuriant growth in separation and under circumstances of the utmost
difficulty; and thus it was, that Nicholas, thinking of nothing but
the unknown young lady, from day to day and from hour to hour,
began, at last, to think that he was very desperately in love with
her, and that never was such an ill-used and persecuted lover as he.
In other news, as is my wont in marking events of great significance, here's some crypto: VIBYOR. What did I just do? Nai, Niladri and Ba, this is for you :-)