in. SURVEYING. 751 



of the telescope and the adjusting of the water-level, which easily give'rise to 

 injury, will be rendered superfluous. Other constructors have endeavoured 

 to obtain this result by the employment of double-cut water-levels ; ' a correct 

 construction, however, of such instruments is very difficult, and any errors 

 incurred cannot be corrected. . 



3046. Patent Level. A combination of the V and Dumpy 

 patterns. ' Patrick Adie. 



3045. Theodolite-Level. A combination of the two instru- 

 ments. Patrick Adie. 



3O46a. Dumpy Level, of improved construction. 



Joseph Casartelli. 



With graduated circle, for taking horizontal angles, and ball-and socket 

 motion greatly facilitating its adjustment, especially on hilly or uneven ground, 

 and saving the wear of the adjusting screws. The instrument being made of 

 hard gun-metal, and the centre being long and accurately ground, renders it 

 little liable to derangement. 



3086. Levelling Instrument. 



Meissner, Berlin (If. Muller and F. Reinecke). 



This levelling instrument is distinguished by its simple and unchangeable 

 Arrangements for correction. 



3089. New Levelling Instrument, constructed by A. 

 Geppert, completed by F. Miller. F. Miller, Innsbruck. 



This instrument is adapted especially for surveyors and engineers in 

 mountainous countries. The arrangement is as follows : The vertical 

 axis is placed perpendicularly by means of 4 screws. It is provided with a 

 horizontal graduated circle reading by means of a vernier, to two minutes. 

 The astronomical telescope magnifies 15 times, and is capable of 14 degrees 

 of depression or elevation. The inclination of the telescope is measured by 

 a micrometer screw. Its uses are : Direct and indirect levelling, measure- 

 ment of height and distance, horizontal angles, &c., and plotting the same. 



3 104. Abney's Level. The instrument was designed by Capt. 

 Abney, R.E., F.R.S., for military reconnaissances. It measures 

 vertical angles by means of a spirit level attached to a graduated arc, 

 which is capable of moving round an axis. The object whose angle 

 of depression or elevation is to be ascertained, is brought into the 

 field of view, and the spirit level is then moved till the bubble is in 

 the centre. When in this position the bubble is seen in a reflector 

 placed in the body of the tube ; an opening being left for the 

 purpose. Elliott Brothers. 



3105. Elliott's 14-inch improved Dumpy Level, with com- 

 pass for taking levels and bearings. Elliott Brothers. 



This instrument, being provided with an object glass of large aperture and 

 short focal length, and sufficient ligh't being thus obtained to admit of a 



