3. To convert Réaumur degrees into degrees of Fahrenheit, multiply by 9, divide by 4, and add 32.[[6]]
4. To convert Réaumur degrees into degrees of Centigrade, multiply by 5 and divide by 4.[[7]]
[6]. 8 R = 50 F.
[7]. 8 R = 10 C.
For the production of continuous records, the Meteorological Committee of the Royal Society have adopted an instrument called a Thermograph, or self-recording wet and dry bulb thermometer, which is largely aided by photography. The bulbs of the thermometers are necessarily placed in the open air, and at a suitable distance from any wall or other radiating surface; the tubes are of sufficient length to admit of their being brought inside the building, in due proximity to the recording apparatus placed in a chamber from which daylight is rigidly excluded.
19.
Thermograph and Self-recording Hygrometer.
Scale about 1/18.
The essential conditions in such an apparatus are:—1. A means of denoting the height of the mercurial column in the stem of a thermometer in relation to a fixed horizontal line. 2. A time scale denoting the exact moment at which the atmosphere reached the temperature indicated by the mark. 3. As the marks are produced chemically, and not mechanically (as in the Anemograph), a dark room.