On the picturesque

"... Now,  I  have  insisted  long  on  this  English  character, because I want the reader to understand thoroughly the opposite element  of  the  noble  picturesque:  its  expression,  namely,  of suffering, of poverty, or decay, nobly endured by unpretending strength  of  heart.  Nor  only  unpretending,  but  unconscious.  If there be visible pensiveness in the building, as in a ruined abbey, it becomes, or claims to   become,   beautiful;   but   the   picturesqueness   is   in   the unconscious suffering.

...their  merely  outward  delightfulness—that  which  makes  them  pleasant in painting, or, in the literal sense, picturesque—is their actual variety of colour and form. A broken stone has necessarily more various forms in it than a whole one; a bent roof has more various  curves  in  it  than  a  straight  one;  every  excrescence  or  cleft  involves  some  additional  complexity  of  light  and  shade,  and   every   stain   of   moss   on   eaves   or   wall   adds   to   the delightfulness  of  colour.  Hence,  in  a  completely  picturesque  object, as an old cottage or mill, there are introduced, by various circumstances  not  essential  to  it,  but,  on  the  whole,  generally somewhat detrimental to it as cottage or mill, such elements of  sublimity—complex light and shade, varied colour, undulatory  form, and so on—as can generally be found only in noble natural
objects, woods, rocks, or mountains."

Modern Painters IV