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Ther′mo-graph.

An instrument for automatically recording variations of temperature.

In the apparatus, Fig. 6350, this is effected by means of photography. The instrument when in use is inclosed in a box, and all light is excluded except that which is admitted through an air-speck in each thermometer. g is a cylinder on which the photographic paper is wound, and is rotated by clock-work h once in forty-eight hours; i, shutter cutting off the light for four minutes every two hours, and leaving a white line when the paper is developed; s, wet-bulb thermometer; t, atmospheric thermometer; b, screw for adjusting thermometers to the required hight; c c, gas-lights; d d, condensers throwing the light on to the mirrors r r through air-specks in the thermometers, the light passing through slits e e; f f, photographic lenses throwing an image of the air-speck in each thermometer upon the paper on the cylinder g, and leaving two irregular dark lines corresponding to the varying hights of the wet-bulb and atmospheric thermometers.

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