VIII. CHRONOGRAPHS. 369 



spectrum had been taken on silver chloride and bromide, which had been 

 made sensitive to the less refrangible rays through addition of light-absorbing 

 media. 



lS54a. Sun spots photographed at Wilna with Dallme- 

 yer's Heliograph. The Observatory, Wilna. 



These photographs are made with the Dallmeyer heliograph, constructed for 

 the Observatory of Wilna, on the designs of De la Rue. Six of these belong 

 to the period of maximum of sun spots in September 1870, 12 other represent 

 the largest sun spots observed during the years 1871-1875. Similar photo- 

 graphs are made at Wilna every bright day, under the direction of Colonel 

 Smysloff, for promoting the study of the surface of the sun. 



1865. Photographs of different parts of the Sun's 

 spectrum. 



Dr. If. C. Vogel and Dr. Chr. Lohse, Potsdam. 



1866. Photographs of the Sun. 



Dr. H. C. Vogel and Dr. Chr. Lohse, Potsdam. 



1867. Photographs of Jupiter. 



Dr. H. C. Vogel and Dr. Chr. Lahse, Potsdam. 



1868. Drawing of the Spectrum of the Sun between 

 Fraunhofer's lines H 1 and H 2 , made from a photograph. 



Dr. H. C. Vogel and Dr. Chr. Lohse, Potsdam. 



1869. Specimens of Photographical Multiplication and 

 Reversion of astronomical drawings of nebulre and comets (Dr. 

 Voxel's method). 



Dr. //. C. Vogel and Dr. Chr. Lohse, Potsdam. 



1870. Lunar and Solar Photographs. Warren de la Rue. 



1870a. Enlarged Solar Photographs, by Mr. Rutherford 

 of New York. J. Norman Lockyer, F.R.S. 



VIII. CHRONOGRAPHS. 



1871. Wheatstone's Magnetic Chronograph, for mea- 

 suring very small intervals of time. 



Wheatstone Collection of Physical Apparatus, King's 

 College. 



1872. Groves *s Chronograph, for astronomical calculations, 

 for railway speed, and speed of machinery. W. Groves. 



1873. Yvon Villarceau's Astronomical Chronograph. 



Exhibited by Breguet. 

 39508. A a 



