Medical history of the expedition to the Niger during the years 1841-2, comprising an account of the fever which led to its termination / by James Ormiston M'William.

Date:
1843
Catalogue details

Licence: Public Domain Mark

Credit: Medical history of the expedition to the Niger during the years 1841-2, comprising an account of the fever which led to its termination / by James Ormiston M'William. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    arrived in the Niger. The letter f represents the fanner or ventilating machine, receiving the vitiated air from the various compartments of the ship, and discharging it at s. A fanner operates essentially by disturbing the equilibrium of the pressure of the atmosphere. As the blades revolve, the air in immediate contact with them is conveyed towards their extremities by the centrifugal force, and propelled at any opening in the circumference s. In this manner a com- parative void is left within the casing of the fanner, and the tubes connected with the different com- partments communicating freely between them and the interior of the apparatus, the pressure of the external atmosphere forces air from them to restore the equilibrium, and this process goes on incessantly so long as the motion of the fanner is sustained. The fanner was put in motion by the machinery connected with the steam-engine. It was also oc- casionally worked by the Kroomen, and in general during the night, when in the river, by the stream, as when the engine was disconnected with the pad- dles they were moved by the current, the paddles in this case acting as water-wheels, and the force thus obtained was applied to the movement of the fanner. Letters e e indicate the principal distribution tubes which extended fore and aft throughout the ships. They may be compared to the great arteries or