Quartz Spectrographs

E 3

The following two spectrographs, with quartz prisms and lenses, have been very carefully designed with the following objects in view:—

(1) To be in permanent adjustment.

(2) To give the whole spectrum from 200 µµ to 800 µµ on one plate.

(3) To give good definition over the whole spectrum on the ordinary photographic plate.

(4) To give as large an amount of light as is consistent with the above conditions, thus enabling spectrograms to be taken with relatively short exposures.

The instruments are sent out completely adjusted, ready for photographs to be taken.

Fig. E 3.

Quartz Spectrograph, size (c) (see Fig. E 3).—Lenses of 24 inches (610 mm.) focus, the instrument giving a spectrum from 210 µµ to 800 µµ of about 200 mm. long. Prism, 41 mm. high x 65 mm. long face. Size of plate, 10 x 4 inches. The slit is our No. 2 (see Spectroscope slits, Section F). The dispersing system consists of one Cornu prism. There is a vertical motion by rack and pinion to the dark slide, with scale, whereby a number of exposures can be taken one below the other.

Price

£58 15 0

(Specimen photographs will be sent post free on application.)

Quartz Spectrograph, size (c), with wavelength scale.

In the case of the size (c) instrument, an accurate scale of wavelengths can be mounted internally in such a manner as to be brought at will in contact with the photographic plate. Illumination is provided by means of a small electric lamp, and a contact print of the wavelength scale can thus be obtained on the same plate as, and in juxtaposition to, the photograph of the spectrum (as in Fig. E 1).

Price, if ordered at the same time as the spectrograph, including small battery in case, with push key for illuminating lamp; the whole being attached to the spectrograph in a convenient position for use £13 0 0

The accuracy with which wavelengths can be read on these scales is approximately as follows:—

<table><thead><tr><th>WAVELENGTH.</th><th>ERROR OF READING.<br>(In Ångström units.)</th></tr></thead><tbody><tr><td>7000</td><td>100</td></tr><tr><td>4000</td><td>20</td></tr><tr><td>3000</td><td>5</td></tr><tr><td>2500</td><td>2</td></tr><tr><td>2200</td><td>1</td></tr></tbody></table>

If desired, the scales can be divided to read frequencies instead of wavelengths, the price being the same.

ADAM HILGER, Ltd., 75a Camden Road, London, N.W.