The spectroscope and its applications / by J. Norman Lockyer.

Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: The spectroscope and its applications / by J. Norman Lockyer. 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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    of the sun. One peculiarity of the instrument in Fig. 33 is that the ray of light having passed once through the lower part of the train of prisms, is received by a right-angled prism, which totally reflects the light twice, sending the ray of light back through the upper part of the same prisms, when it is again refracted; we thus have, by using these prisms, the same effect as if thirteen prisms had been employed. The ray of light enters the instrument by the lower tube, and after Fig. 32.—Sun Spectroscope, d. Collimator ; Observing telescope ; h and M, Two micrometers ; i, 2, 3, 4, 5, 6, 7, Prisms. passing first through the lower half of the prisms, and back through the upper half, is received in the upper tube, and reflected upwards for convenience of observation. These prisms are so arranged, that whatever part of the spectrum is being observed, they are always at the angle' of minimum deviation