Gravity pulls it downstream. All of it. Every drop of water merging into a river, whether fallen directly from the clouds into a small brook, or bubbling from a spring seep on a large and open river, is under the consistent influence of a force none of us can see. But we feel it. It’s predictable. Gravity holds few surprises. And though its mystery runs deep, we’ve each learned, from birth, to expect the unseen force holding our world together to continue doing just that — to keep all the pieces and parts stuck tight — trusting that the center will hold and things won’t fall apart. It’s consistent enough to be boring. But as an angler, the effects of gravity on flowing water is fascinating. It’s fundamental. And it’s the key to reading trout water . . .