River in the Catskills, 1843, Thomas Cole
When I look at this painting I notice the sunlight and the range of colors between the foreground, middle ground, and background. There are rolling hills and mountains in the background and a small village near the center of the painting. Cole clearly uses the S curve in the form of the river to guide the eye into the distance and create depth. The blueish tint on the mountain also imitates depth through atmospheric perspective. Cole also makes the the objects appear much smaller the farther away they are. For example, the trees in the middle ground are quite a bit larger than the trees on the hills in the background.
The Rocky Mountains, Lander's Peak, 1863, Albert Bierstadt
In this painting I notice the large mountains in the background sort of looming over the rest of the scene. I also notice the waterfall in the background that leads into a larger lake near the herd of animals and people. Bierstadt uses atmospheric perspective to create depth by making the mountains more blue and hazy than the rest of the painting. The use of overlapping with the trees also creates a sense of a boundary between the middle ground and the background. Bierstadt also uses differing sizes with huts near the trees being smaller in size than the huts that are towards the right. There also seems to be a slight S curve near the waterfall leading up the mountains.
An underpainting is a layer of paint first applied to a canvas as a base for the rest of the painting. Underpainting can be used to create initial tonal values and have an effect on the later mood and colors. Blue toned underpaintings are better for wintery or cool toned paintings whereas yellow toned underpaintings are better for hot or warm toned paintings. One type of underpainting is the tonal grounds underpainting where you paint the entire canvas one color to create backlighting shadows. Another type of underpainting is A tonal underpainting used to map out where the dark and light areas will be. Using A tonal underpainting can create brighter top colors and make developing the subject easier later on.