An awareness of the significance of location in the production and dissemination of scientific knowledge has brought a new dimension to recent work on the sociology of science. But the importance of speech in scientific enterprises has been less well developed. This article explores the idea of `spaces of speech' by underscoring the connections between location and locution. It develops a case study of how Darwinian evolution was talked about in different sites using examples from Ireland and the American South (...) during the latter part of the 19th century. These reveal how sites enable and constrain what may be said, and heard, about particular scientific claims, and how they are crucial to understanding the circulation of scientific claims in public arenas. (shrink)