HI. MISCELLANEOUS. 633 



higher magnifying .power in the eye-piece, the advantages of a much larger 

 instrument are obtained. A mirror is placed in the bubble, so that the 

 operator can see, while reading the levelling staff', if the instrument keeps its 

 proper position ; this being necessary on soft and spongy ground. 



3105a. 14-in. Dumpy Level, with improved rack adjust- 

 ment to cross webs. Henry Porter. 



3106. Repeating Theodolite. 



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



The repeating theodolite has the advantage of the particular firmness of 

 the telescope supporter. 



3106a. Quadrant used by Captain Cook during his several 

 voyages. Richard Caulfield, LL.D., F.S.A., Cork. 



3107. Sextant, by Rams den. Prof. Winnecke, Strassbtirg. 



3107a. Improved Bos or Pocket Sextant. To enable 

 the observer, when sounding from a moving boat or vessel, to 

 "take both angles in fixing a position without delaying to read off 

 one angle before taking the other. 



Captain J. E. Davis, R.N., F.R.G.S. 



This is effected by means of a supplementary arm and vernier, not affected 

 by moving the proper arm' unless connected by means of the hook and pin. 

 When connected the vernier of the supplemental arm corresponds with that of 

 the other vernier minus 20 degrees. 



When used the arms are connected, and the larger angle is taken first, the 

 hook is then pushed back, and the supplemental arm remains to record that 

 angle, which is read off" after the small angle is taken. 



Particularly useful when fixing positions in sounding and the boat or vessel 

 is moving quickly. 



31O7b. Improved Sounding Sextant. To enable the ob- 

 server, when sounding from a moving boat or vessel, to take both 

 angles in fixing a position without delaying to read off one angle 

 before taking the other. Captain J. E. Davis, R.N., F.R.G.S. 



When used the pawl of the indicator is attached to the movable arm and 

 moves with it. When the larger angle has been taken the finger is applied 

 to the capstan-headed screw, which at once clamps the indicator and frees the 

 pawl from the arm, the smaller angle is then taken and read off ; the arm is 

 then moved up to the indicator, and the larger angle read off ; the capstan- 

 headed screw is loosened and the pawl drops, connecting the indicator again 

 with the arm. 



3107c. Improved Sextant. For observing and recording a 

 number of observations without the necessity of reading off at 

 the time of observation, or removing the eye from the telescope, 

 effected by means of a micrometer movement affixed to the tan- 

 gent screw, and indicators applied to the arc. 



Captain J. E. Davis, R.N., F.R.G.S. 



This is effected by means of a micrometer movement affixed to the tangent 

 screw, and indicators applied to the arc. 



