404 SEC. 11. ASTRONOMY. 



The spectrum apparatus is constructed on the simple principle which has 

 proved so successful at the Observatory of Bothcamp, with the difference, 

 however, that this apparatus is arranged for absolute measurement, and that 

 the one at the Observatory of Hamburg is attached at right angles to tbe prin- 

 cipal axis of the refractor. 



1804. Spectrum Apparatus, for observing the Solar Pro- 

 minences, to be attached to the collimator of the spectroscope. 



Hugo Schroder, Hamburg. 



This spectrum apparatus, which is in reality a supplement of the first, 

 can be fastened to the collimator of the other one with great readiness. 

 The object of this apparatus is the observation and measurement of the 

 solar spectrum as well as of the solar prominences. The principle on which 

 it is constructed differs from that of the former in that the rays after once 

 passing through the system of prisms do not issue from it in the same direc- 

 tion as they entered, but are refracted and dispersed by the heavy prisms 

 of flint glass. By means of a rectangular prism of crown glass the raj r s are 

 compelled to pass through the system a second time, and leave it in a direc- 

 tion parallel to that of their first entrance. By a second prism of crown 

 glass the rays are reflected into the observing tube which is attached to 

 the prism holder. The movement of the spectrum across the field of view, as 

 well as the absolute measurement, is effected by turning the first prism of 

 crown glass by means of the micrometer screw. This apparatus is, on account 

 of its convenient and highly stable construction, . particularly to be recom- 

 mended for observers who have scanty room at their disposition, and yet wish 

 to undertake accurate measurements. 



1805. Star Spectroscope, after Dr. H. C. Vogel (described 

 in the Berichte der koniglichen sachsischen Gesellschaft der Wis- 

 sensehaften, December 1873). H. Hcustreu, Kiel. 



This apparatus recommends itself for its simple construction, its varied 

 application to all kinds of observations, and its reasonable price. 



1806. Spectroscope made by Merz in Munich. 



Prof. Dr. Winnecke, Strassbtiry. 



18O6a. Parts of a Solar Spectroscope, made by Elliott 

 Brothers in 1869. J. Norman Lockyer, F.R.S. 



In this instrument the prisms are brought to minimum deviation by means 

 of a spring, suggested by Mr. G. W. Hemming, and the light is brought back 

 through the prisms by a total reflection prism at the end of the train, on the 

 plan first employed, it is believed, in this instrument, and suggested by the 

 exhibitor. 



1806b. Solar Spectroscope, with diffraction grating on 

 speculum metal, presented to the exhibitor by Mr. Rutherfurd, of 

 New York. , J. Norman Locki/er, F.R.S. 



1806c. Solar Spectroscope, used since 1868 in observing 

 solar phenomena, made by Browning. 



J. Norman Lockyer, F.R.S. 



1806d. Slit arrangements for Spectroscopes. 



J. Norman Lockyer. 



