The emerging cultures of late nineteenth-century steamship mobility can be distinguished broadly by ocean basin and by specific route. In the Pacific, a steamship connection between Sydney and San Francisco was envisaged to forge and sustain strong bonds between regional 'branches' of the Anglo-Saxon race. This article moves beyond the rhetorical purchase of assumed affinities, to explore the more layered ways in which difference was articulated in transpacific encounters, and the attendant uncertainties and frictions in these evolving relations. When compared to routes bridging the Indian and Atlantic Oceans, with familiar imperial hierarchies and formalities behind them, British and colonial travellers in the Pacific were frequently unsettled by the more democratic and republican attitudes of the American crews and passengers they encountered. At the same time, Britain's long-standing supremacy on the high seas provided a benchmark against which American enterprise and power in the Pacific could be assessed and found wanting.