364 SEC. 11. ASTRONOMY. 



without the current. In other systems, where the current is applied directly 

 to move the wheel-work, a single miss of the current destroys the coincidence 

 of time shown. 



1845. Ancient Sundial, for showing the time in any lati- 

 tude, scale for setting the sun's declination, and equation table. 



Elliott. Brothers. 



1846. Sissons' Universal King Dial, for finding the sun's 

 declination and his place in the ecliptic, the latitude of any place, 

 and the hour of the day. Adam Dixon. 



1847. Two Ring-shaped Equatorial Sundials. 



1848. Two Sundials, with calendars. 



1849. Compass, with Sundial, of the year 1597, with 

 various movable discs for adjusting the zodiacal circle, &c. 



Berggewerkschaftskasse, Bochum, Westphalia. 



VI. SIDEROSTATS. 



1850. Universal Heliostat, designed by Col. Campbell, and 

 executed by Adam Hilger, 192, Tottenham Court Road. 



Lieut.- Colonel Archibald C. Campbell. 



This instrument, after the polar axis has been set due north and south, and 

 adjusted for latitude, will throw the light of a star or the sun in any required 

 direction, and will keep it there by means of the clock ; all the slow motions 

 in altitude and azimuth can be manipulated by the observer without 

 stopping the instrument. The connexions are placed ready to the observer's 

 hand, wherever he may be. 



A small telescope is also attached to the polar axis, so that it may act as a 

 finder for any object, which, when seen in this telescope, will be reflected 

 by the mirror to the required spot. The mirror is 1 foot by 8 inches, and is 

 a perfect plane. This was also constructed by Mr. Hilger. 



Dimensions. Iron stands, 30 ins. diameter ; height, 3 ft. 2 in. to centre of 

 mirror. Mirror, 1 ft. by 8 in. 



1851. 'sGravesande's Heliostat, with his Equatorial 

 Clock. Conservatoire des Arts ei Metiers, Paris. 



185 la. Siderostat, by Foucault. Paris Observatory. 



1851b. Heliostat, by Gamberg. Paris Observatory. 



1851c. Heliostat, by Silbermann. M. J. Duboscq, Paris. 



1851d. Heliostat, by Foucault. M. J. Duboscq, Paris. 



1851e. Photograph of a Siderostat, constructed by 

 Messrs. Cooke and Sons of York, for the Royal Society. 



J. Norman Lockyer, F.R.S. 



