736 SEC. 16. GEOLOGY AND MINING. 



The improvements are additions to the ordinary Miner's Dial or Circum- 

 ferentor, viz. : 1st, a radiating limb and sights worked by rack and pinion 

 attached to a quadrant, for taking vertical angles. 2nd, a similar arrange- 

 ment, working a circular plate with sights and vernier, for taking horizontal 

 angles. 3rd, a circular level, ground to a radius of about 15 feet, fitted inside 

 the dial on the base plate, in lieu of the usual cross levels outside. 4th, 

 fitted into the same case, with sockets screwed to receive three legs either 

 permanent or temporary, is a ball and socket stand, with adjusting rod which 

 enables the instrument to be correctly adjusted almost instantaneously, while 

 the parallel plates are in any position within 25 percent, of the perpendicular. 

 Where the ground to be surveyed is slippery, or the vein thin, with a low 

 roof, and its inclination steep, this arrangement of stand is of great advantag e 

 to correct and rapid surveying. 



3397b. Davis's Improved Clinometer with tripod, which 

 folds up and forms a walking-stick. John Davis and Son- 



This clinometer is much used in geological surveys ; the arc being of a large 

 size, gives by aid of the levels the gradient of stratum very accurately. 



The special arrangement in this instrument is in the stand, also in the large 

 size of the compass, which turns over, rendering the clinometer capable of 

 doing the work of a level and dial approximately. Where great accuracy is 

 not required, it will save time and a more expensive instrument, and on 

 account of its extreme portability may be used when a level or dial could 

 not. Its outside dimensions are, when folded up, 6" by ^ " by 3". 



3397c. Davis's Improved Hedley, Dial, or Circum- 

 ferenter, for mine surveying. John Davis and Son. 



This form of dial is especially used in mines of steep gradient ; the body of the 

 dial remains fixed while the sights move on axes, the arc at the same time gives 

 the gradient or dip of the stratum. The special improvement in this instru- 

 ment is a means of surveying with the vernier and needle simultaneously, 

 which is fully described in the printed form affixed. 



3398. Mine Levelling Lath (Junge's). 



Royal Saxon Mining Academy, Freiberg. 



3399. Collection of various Mine Signals for subterranean 

 measuring of angles with the theodolite. 



Royal Saxon Mining Academy, Freiberg. 



3400. Pocket Compass apparatus with stand. 



F. W. Breithaupt and Son, Cassel (G. Breithaupt). 



34:01. Six-inch Theodolite, with two Telescopes, by Messrs. 



Troughtons & Simms, with adaptations for underground sur- 

 veying, suggested by the contributor. Walter Rowley, C.E. 



3402. Mine Theodolite (No. 159), with stand and leather 

 case. Otto Fennel, Cassel. 



Differs from the preceding principally in the apparatus for adjusting the 

 telescope. 



