Values in a Landscape, part 1

Value! It's a very important part of creating a strong statement in your painting.
What is value? Value is the "darkness" or "lightness" of a color. Here you'll see a value scale, and a simple landscape, which I've posted here in black and white to illustrate some points about value.
You'll see that the value scale is simply a graded rule, going from black,the "darkest dark" to white, the "lightest light". There are, of course, infinite gradations in between, but for ease of use, this scale has 10.
As you can see from the little landscape here, value alone, without color, can portray a believable image. We're all familiar with this concept in black and white photography.
For the next several posts, I'm going to talk a bit about value, and some good simple "rules" that can help to simplify our approach to painting a landscape, and help us to create good strong compositions.
For starters, let's break the value scale into four groups. Let's say, blocks 1 -2 for light, 3-4 for "medium light", 5-6 for "medium dark" and 7-10 for "dark". Now, let's break down the landscape into four major elements. We have sky, land, trees, and hills. For now, forget the cows! Look at the scale, and then at the painting.
Here's your homework. Comparing our value groups on the scale, and the painting, can you find the light, medium light, medium dark, and dark elements? I'll do the first one for you. The "light" element is the sky! Now, you do the rest!
Tomorrow: the "theory of angles" and four planes of light!