194 DEEP BOREHOLE SURVEYS AND PROBLEMS 



clinometer is an eccentrically weighted drum bearing a 

 strip of sensitized paper which rocks close to a diaphragm 

 with apertures in it. 



The magnetic needles and apertures move on one spider 

 and they are encircled by a strip of sensitized paper on a 

 drum and all hght is excluded except at the apertures. 

 On top of this is an opal glass lit up by the lamps which 

 flood the inside with subdued light, and this gives the 

 photographic record of the needles. When horizontal 

 each lamp lights up half of the dome, and when the instru- 

 ment is vertical one lamp lights up the whole dome, so that 

 illumination is constant at all angles. The instrument is 

 best understood if taken part by part.^ 



Figure 1 (Plate XII) shows the complete instrument. 

 At the ends of the external casing 3 are screwed two similar 

 watertight plugs 1 and 55 of non-magnetic material, 

 the latter having the hauling rope eye. The two separate 

 internal carrier tubes 5 and 39 are bayonet jointed for easy 

 removal. In Figs. 1 and 2, on pivots 6 and 21, is a cradle 

 26 with a compass, clinometer and two lanterns. By way 

 of cap bolt 21 a stud 25 makes electrical contact with a dry 

 battery. The weight of the cradle 26 keeps the clinometer 

 in a vertical plane, as in Bawden's method. It is borne 

 on end pivots 7 and 19, and there are two lamps at 35 on 

 the central line of the cradle in front of and behind the com- 

 pass, the one always throwing light on the clinometer 

 holes. These lamps are connected in parallel to bolts 20 

 and contact finger 57. 



The clinometer 27 (Figs. 2, 3) is a drum on a spindle free to 

 revolve at right angles to the cradle pivots and has oil 

 damping in its bearing sleeves; and behind are spring clips 

 9 for the record paper 10. On its side next to the compass 

 is the aperture plate 11. 



The magnetic compass is spherical and borne on pivots 

 63 at right angles to the cradle pivots (Figs. 2, 4). Its 

 lower half 33 is sohd, thus being the righting weight which 



1 Dr. J. S. Owens's paper read before the Institute of Mining and Metal- 

 lurgy, Jan. 21, 1926. 



