VII. PHOTOGRAPHY. 367 



1856. Apparatus for the production of Photographs of the 

 Sun, after Dr. Oswald Lohse. A. Fuess, Berlin. 



1857. Stand with Equatorial Motion about a vertical and 

 horizontal axis for a photographic lens of 6" aperture, used by the 

 German expedition to Kerguelen's Island, for the observation of the 

 transit of Venus, 1874. (Photograph.) 



A. Repsold and Sons, Hamburg. 



The point of intersection of the horizontal and vertical axis produced 

 is at the same time the centre of movement of the equatorial system, which 

 consists of an hour axis and a declination arc. This arc is suspended from a 

 double arm fastened to one end of the horizontal axis parallel to the telescope, 

 revolving about it, and concentric with the centre of motion. As it is tied to 

 the head of the hour axis, and revolves with it, it compels the double arm, and 

 at the same time the telescope, to move equatorially about the horizontal and 

 vertical axes. By this arrangement the position of a thread in the focus of 

 the object glass can always be controlled by the level attached to the telescope. 

 (See P. A. Hansen, " Beschreibung eines Fernrohrstatio's," &c., in the 

 Berichten der Kgl. sachisch. Ges. d. Wiss. Mathem. Phys. A., 1 Jul. 1870.) 

 To enable the telescope to follow the daily movement there is a screw moved 

 by connexion with the clockwork. 



1858. Small Spectrograph. Simple apparatus for taking 

 the sun's spectrum, consisting of a camera (without objective), 

 and a Browning's pocket spectroscope. 



Professor H. W. Vogel, Berlin. 



The small spectrograph serves for studying the chemical effect of the 

 different parts of the solar spectrum upon substances sensitive to light, 

 and for ascertaining the varying intensities of the various parts of the solar 

 light at different places and times. The slit is wedge-shaped, in order to 

 have more light at one end of the spectrum than at the other. The more 

 intense the chemical effect of a colour, the further it reaches towards the dark 

 end of the spectrum. The apparatus is held in the hand, and so directed 

 upon the Sun that the spectroscope may throw no shade. No heliostat is 

 required. The exhibitor has been able to use the instrument on board ship, 

 whilst sailing from Brindisi to Ceylon. (Pogg. Ann., Bd. 156, p. 321.) 

 The exhibited apparatus has been made by Schmidt and Haensch, Berlin. 



1859. Specimen Impression made with the before-men- 

 tioned apparatus. Professor H. W. Vogel^ Berlin. 



b. PHOTOGRAPHS. 



1860. Astronomical Photographs : 



a. The moon, enlarged to 80 and 100 inches diameter by the 



new re-photographing process. 



b. The solar corona and its spectrum, photographed with short 



foci mirrors and objectives. 



c. Solar spots, enlarged 100 times by the " Universal" Micro- 



scope, designed by Prof. Zenger, and made by Schieck, of 

 Berlin. 



Professor Carl Wenzel Zenger, Prague. 



