I. SURVEYING. 609 



Constructed by Messrs. Troughton and Simms. Telescope, aperture 3^ 

 inches, focus 36^ inches. Horizontal circle, diameter 3 feet. Vertical circle. 

 2 feet. (Photograph about real size.) No. 1. General perspective view. 

 No. 2. Elevation in plane of pillars. No. 3. Side elevation, showing vertical 

 circle and microscopes. No. 4. Side elevation, showing counterpoises of 

 vertical circle and microscopes. No. 5. Horizontal circle (plan of upper sur- 

 face). Vertical axis socket. Horizontal microscope arms, &c. (plan of under 

 surface). No. 6. Horizontal circle (plan of under surface). Table, pillars, 

 horizontal microscope arms, &c. (plan of upper surface). 



2967. Photographs of the Zenith Sector for the great 

 trigonometrical survey of India. Designed by Lieut.-Colonel 

 A. Strange, F.R.S. 



Constructed by Messrs. Troughton and Simms. (Telescope, aperture 4 

 inches, focus 4 feet. Sector, diameter 3 feet.) (Photograph about |- real 

 size.) No. 1. Front elevation, complete. No. 2. Front elevation, telescope 

 and sector removed. No. 3. Back elevation, complete. No. 4. Side eleva- 

 tion, complete. No. 5. Telescope and sector (side elevation). Plinth (plan 

 of inner surface). Vertical axis. Cradle, with microscopes and levels 

 (plan). 



2968. Photographs of the Electro-Chronograph for the 



great trigonometrical survey of India. 



Constructed by M. Elevens and M. Hardy, of Paris, under the superinten- 

 dence of Lieut.-Colonel A. Strange, F.R.S. , assisted by M. Leon Foucault, 

 member of the Institute. (Photograph about |- real size.) No. 1. Front 

 elevation. No. 2. Back elevation. No. 3. End elevation, showing clock work. 

 No. 4. End elevation, showing connexion of pointer slide with barrel. No. 5. 

 Plan of upper surface-barrel removed. 



2969. Photographs of the Transit Instrument for the 



great trigonometrical survey of India. Designed by Lieut.- 

 Colonel A. Strange, F.R.S. 



Constructed by Messrs. T. Cooke and Sons. Telescope, aperture 5 inches, 

 focus 5 feet. (Photograph about -jL real size.) No. 1. General perspective 

 view. No. 2. Elevation in plane of telescope. No. 3. End view of transit 

 axis and levels. No. 4. Front view of transit axis and levels. Bearings and 

 their foundation plates (plan of upper surfaces). No. 5. Bearings and their 

 foundation plates (side and inner elevations). 



20 7O. Photographs of the Diagonal Transit Instru- 

 ment for the great trigonometrical survey of India. 



Constructed by Messrs. T. Cooke and Sons, under the superintendence of 

 Lieut.-Colonel A. Strange, F.R.S. Telescope, aperture 2 '64 inches, focus 

 34-6 inches. (Photograph about real size.) No. 1. Elevation in plane of 

 telescope. No. 2. Telescope raised for reversal. 



2971. Photographs of the Vertical Circle for the great 

 trigonometrical survey of India. 



Constructed by M. M. Repsold, of Hamburg, under the superintendence of 

 Lieut.-Colonel A. Strange, F.R.S. Telescope, aperture 1-9 inch, focus 

 18 -8 inches. Vertical circle, diameter 12 inches. (Photograph about | real 

 size.) Front and side elevations. 



39508. 



