sill was the subject of biographies by william belmont parker in 1915 and by alfred riggs ferguson in 1955. according to the "encyclopædia britannica" eleventh edition, "he was a modest and charming man, a graceful essayist, a sure critic. his contribution to american poetry is small but of fine quality. his best poems, such as "the venus of milo", "the fool's prayer" and "opportunity", gave him a high place among the minor poets of america, which might have been higher but for his early death."