The tendency to magnify the moment, to read all the laws of Nature in the one object or one combination under your eye, is of course comic to those who do not share the philosopher's perception of identity. To him there was no such thing as size. The pond was a small ocean; the Atlantic, a large Walden Pond. Ralph Waldo Emerson, "Thoreau" The term "luminism" has become popular with recent historians of Ameri- can art, but it still remains elusive and problematical.1 Unlike equally slippery "isms" such as "Romanticism" and "Impressionism," it was not originally adopted by the artists to which it has been applied, but rather was coined one hundred years after the fact to describe a special quality of their work. John I. H. Baur first formulated the term in a pioneering article entitled "American Luminism: A Neglected Aspect of the Realist Movement in Nineteenth-Century American Painting," published in 1954.2 Here Baur identified this forgotten phase of native art, primarily concerned with the detailed recording of the effects of light, as a movement which ''reached its fullest expression in the I850's and 60's, particularly in the work of two men, Fitz Hugh Lane and Martin J. Heade" (p. 92). Thus luminism is an imposed rather than organic category, and though it may sometimes seem as mysterious as an outbreak of measles-appearing in some of a particular artist's paintings but not in all or most of them—I still believe that it describes something real and measurable.