while if you looked down from a hill you 'd have thought it a fine and easy land , green and good to look on , when you were actually down there in the middle of it , tree roots tripped you , sudden rocky spurs cut you off from the next valley , marshy bottoms proved impassable ( though you did n't find out till you 'd already nearly gone too far , and got wet up to the waist by falling in one of the mud wallows or hidden sinkholes ) .