No. Ic, Style p. 



As made by C. L. Berger & Sons 



Taehymeter.* 



Horizontal Verniers in 

 line with Telescope. 



No. 1 c, Style p. Graduations of horizontal and vertical circles on solid 

 silver, reading to minutes; 5-inch full vertical circle with two double opposite 

 verniers reading to minutes; glass shades over verniers; 3 inch striding level ; 

 gradienter attachment ; fixed stadia wires ; etc. Standards cloth finished. 



Price, as above, $3OC.OO. 



For size and particulars, as well as for extras see pp. 142-145. 



This instrument without a striding level, ...... less, $20.00 



" double opposite verniers for vertical circle, " $20.00 



NOTE. In this instrument the verniers of the horizontal circle are placed in the direction of the line of sight 

 of the telescope, so that angles can be read from the position of the observer, without stepping aside. Unfor- 

 tunately, in order to carry this out in instruments provided with a compass upon the upper plate, it becomei 

 necessary either to shorten the front plate-level, which is the principal level in the Engineer's transit, and 

 therefore should always be of standard length and character ; or to raise it above the vernier, in an exposed 

 position, where it will so shade the vernier, as to make the latter almost worthless ; or, as in the cut above, to place 

 the front plate lvel entirely outside of the plates, where his ;ilso in an exposed position, and is liable to de- 



by a gu 



rangement though protected from breakage by a guard. A third arrangement, to place the level inside, but 

 the compass bottom, requires that the space between the plates be increased, thereby raising the height of the 

 whole instrument about % inch, and increasing the weight ; at the same time the openings in the upper plate 

 weaken the latter and its stability to resist the rough treatment it is liable to receive in the field ; and shorten- 

 ing the plate levels and decreasing their sensitiveness to such an extent as to make them but little better than 

 the circular levels formerly used with the most ordinary instruments. None of these devices can therefore be 

 regarded as a real improvement, except for the more ordinary instruments, where sometimes under certain con- 

 ditions greater accuracy may be considered of lest importance than greater convenience. In instruments with- 

 out a circular compass upon the up;.cr plate, as shown on page 179, this device can be carried out to perfection. 

 A striding level should always accompany this instrument. 



Reading glasses cannot be attached to the horizontal circle of this instrument. The glass shades on this 

 instrument will often prove an obstacle in making solar observations when a prism attachment must be used. 



* See remark on page 147. 



