On 27th November 1861, eleven wardroom officers of the “Marlborough,” including the author, were simultaneously attacked with extreme faintness, nausea, bilious vomiting, and diarrhœa; the attacks lasting five or six hours—in some of the cases being of great severity, and attended with much depression. The treatment, which was successful in every instance, consisted in encouraging free vomiting, and the administration of stimulants and anodynes. At the same time a series of similar cases occurred in H.M.S. “Agamemnon,” and five other ships in the harbour.