advantage in being able to act on all the squares of either
colour is balanced by the fact that the Bishop can sweep long
diagonals. Two Bishops are, generally speaking, of greater value
than two Knights, because together they also act on all the
squares, and their command of long diagonals is a clear
advantage. The whole of this valuation, however, comes to nought
when the pieces are hindered in their mobility by the peculiarity
of any particular position.

We will consider one instance from end-game play, and one from
the openings.

In Diagram 13, White derives no advantage from being

---------------------------------------
8 | | | | | | | | |
|---------------------------------------|
7 | | | | | | | #K | |
|---------------------------------------|
6 | | #P | | | | #P | | |
|---------------------------------------|
5 | #P | | #P | | #P | ^P | #P | |
|---------------------------------------|
4 | ^P | | ^P | #Kt| ^P | | | |
|---------------------------------------|
3 | | ^P | | ^R | | | ^P | ^K |
|---------------------------------------|
2 | | | | | | | | |
|---------------------------------------|
1 | | | | | | | | |