Mid 19th century artists, for the first time, could now take their oil paints with them in tin tubes to paint the unique beauty and power of nature. These artists were now able to break out of the confinement of their studios and carefully observe the dramatic effects of light and shade in vast untouched landscapes around them. They carried with them portable easels, but some of them took plein air painting one step further. The ingenuity of American artist William Preston Phelps, for example, led him to build a horse-drawn mobile shelter that he used for protection from the elements while he painted. Phelps was fascinated by the infinite tints of white, brown, and blue that he perceived in the winter landscape, believing that they required a keen eye for color than do those of spring and summer. Whatever season these artists captured, their uplifting atmospheric depictions of nature are clearly evident in their compositions.