184 



Transit - Theodolite. 



As made for the I . 8. Corps of Engineers. 



Two of these instruments, shown in the accompanying engraving, were designed 

 and constructed for use in the Geographical Exploration and Survey West of the 

 one-hundredth meridian, and exhibited at the Centennial, in the United States 

 -Government Building, by Lieut. George M. Wheeler. 



No. 13 and No. 14 represent this instrument as used in the field for triangu- 

 lation, and as used for astronomical observations. It is designed to combine in a 

 portable form of construction, the efficiency for field use usually obtained with the 

 .larger classes of instruments. 



Horizontal limb is 8 inches in diameter, opposite verniers reading to 10"; vertical 

 circle 5 inches in diameter, opposite verniers reading to 20" ; object-glass \Yz inches 

 clear aperture ; focus 11 inches ; powers of two direct eye-pieces respectively 30 

 and 40 diameters ; power of diagonal eye-piece 40 diameters ; spirit-level attached 

 to telescope and striding level capable of reading to seconds of arc; three leveling 

 screws ; split-leg tripod ; low standards are cast on vernier-plate ; two extra stand- 

 ards for astronomical observations; 3^ inch needle; round level for vernier-plate ; 

 spider-line micrometer ; instrument is ribbed throughout ; lamp, arm and adjustable 

 plane reflector ; sunshade; adjusting pins; case and strap. 



The weight of whole instrument is 14% Ibs. ; weight of tripod 8*4 Ibs. 



Price $C5O. 



Theodolite. 



No. 14. Price of instrument, same in size as that above, arranged for 

 triangulation only, without extra standards, diagonal eye-piece, etc. . 425. 



