DIY History | Transcribe | Scholarship at Iowa | Eccentricity of the Sextant by Frederic Furbish, 1893 | Eccentricity of the Sextant by Frederic Furbish, 1893, Page 49

The artificial horizon.
On land where the horizon is broken by hills and trees a device has to be resorted to in sextant work known as the artificial horizon.
The practical application of the artificial horizon depends upon the law of reflection:- The angle of incidence equals the angle of reflection -- and upon the fact that the angle between a body and its image as reflected in a polished, plane, horizontal surface is equal to twice the angle of the body with the true horizon. This is shown in the following [Cut?] and explanation, --
Let H0 and Hh = parallel rays from a star. [x?] = a reflecting [illegible]. By the law of reflection i = r. By geometry B = i & a = r.

The artificial horizon.
On land where the horizon is broken by hills and trees a device has to be resorted to in sextant work known as the artificial horizon.
The practical application of the artificial horizon depends upon the law of reflection:- The angle of incidence equals the angle of reflection -- and upon the fact that the angle between a body and its image as reflected in a polished, plane, horizontal surface is equal to twice the angle of the body with the true horizon. This is shown in the following [Cut?] and explanation, --
Let H0 and Hh = parallel rays from a star. [x?] = a reflecting [illegible]. By the law of reflection i = r. By geometry B = i & a = r.