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Spectroscopy was introduced as an analytical method in the 1860s. A slit and a collimator is used to collect a parallel beam of light emitted by a substance or from a broad spectrum light passed through an absorption medium. The beam is dispersed by a prism or a grating. The resulting spectrum, emission or absorption, is then observed through a telescope or projected on a screen or photographic paper.


John Browning spectrometer


The principal dispersive medium: the prism. This one was presented to me like a cutlery holder.

prism casing

...although it had this beautiful casing. I fantasize that Newton and Huygens carried such philosophical apparatus in their pockets and once in a while stared at the emerging beam of coloured light.

Above, prism spectroscope by John Browning, 63 Strand London c1870. The instrument is 12 inches high, overall length is 31 inches. The telescope and collimator are 13 inch long . The entrance slit is large. Telescope has a scale and vernier to measure the dispersion of the light coming from the prism.

At right a high quality, unmarked spectroscope.

No name


BL spectroAO Spencer's student spectroscope



At left, an AO Spencer's student spectroscope. It can use either a prism or grating to produce the spectrum. In this spectrometer the prism table, the collimator, and the telescope positions may be determined relative to a high resolution graduated circle. The instrument can be used for the determination and analysis of spectra, in the measurement of angles between prism faces, the determination of angles of refraction and reflection.


The quartz spectrograph at right, was manufactured by the British firm of Adam Hilger, Ltd.,and was used by American spectroscopists in the 1930s.

Light is passed through or emitted from a chemical substance and enters the apparatus through a miniature variable slit. The entrance slit has a comparison prism which can be used to compare two spectral sources at the same time (see image bellow). The dispersive "medium" is located in the elbow at the end of colimating tube.

An identical instrument exist in Caltech scientific instrument collection and Sanko Collection of Physical Apparatus.

Below, the entrance slit with the comparison prism in the Higler spectrograph above; very similar to the entrance slit in some Browning spectrometers


Adam Hilger Spectrograph


prism and slit

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