886 



SECTION XX. 



WEST GALLERY, UPPER FLOOR, ROOM ( O 



COLLECTION OF APPARATUS AND PHOTOGRAPHS 

 ILLUSTRATING ITALIAN SCIENCE. 



4552. Photographs representing various Scientific 

 Instruments in the Observatory of the Collegio Romano, Rome. 



Padre Secchi, Director, Rome. 



No. 1. Spectroscope applied to the refractor of Merz, provided with a net- 

 work by Rutherford. 



No. 2. Spectroscope with network, applied to the refractor of Merz, with 

 the cover adapted to the plate of the network. 



No. 3. Spectroscope with five prisms, with double passage of the ray by 

 reflection, and with automatic movement to bring within the eye-piece the 

 various dispersed rays. 



No. 4. Spectroscope with three angular prisms, and one with direct vision, 

 enclosed in the collimator. 



No. 5. Large objective prism of Merz, of 6 inches, for the spectral analysis 

 of the stars. 



No. 6. Meteorograph of Padre Secchi. 



No. 7. Curves traced with the meteorograph. 



4553. Drawings, on a large scale, of the Meteorograph of 



Padre Secchi, with printed description annexed. 



Observatory of the Collegio Romano, Rome; Director, 

 Padre Secchi. 



4554. Photograph of the Vertical or Zenith Telescope, 



for the observation of stars culminating near the zenith. 



Prof. Lorenzo Respighi, Director of the Royal Observatory 

 of the Campidoglio, Rome. 



The vertical or zenith telescope is intended for the measurement of the 

 zenith distance of stars culminating near the zenith, with the use only of 

 the wire micrometer and mercurial horizon, without need either of inversion 

 or level. The telescope being directed towards the nadir, on the reflecting 

 horizon placed at a great distance bejow the object-glass, it is possible 

 simultaneously to determine the nadir or the first vertical with a fixed equa- 

 torial thread, and to collimate, with the movable thread, the reflected image of 

 the stars that cross the meridian in the field of the telescope, and then to 

 measure the zenith meridian distance with the micrometric screw. In order 

 that the observation may be completely normal, it is necessary that the reflec- 

 tion of the stellar rays extend over the whole object-glass, which will be 

 effected when the distance D of the reflecting horizon from the object-glass of 



the telescope satisfies the condition D == where A is the aperture of 



2 tan Z, 

 the object-glass, and Z the zenith distance of the star. 



In Table VI. is photographically represented the zenith telescope of 

 the Royal Observatory of the Campidoglio, constructed by Signer Ertel of 



