140 DEEP BOREHOLE SURVEYS AND PROBLEMS 



independent setting and adjusting mechanism shown at 

 m (Fig. 2) ; its dial n can be graduated to represent any 

 number of hours, preferably a number not much exceeding 

 the maximum time of its employment. The clock is, as 

 said, controlled automatically and capable of wide and 

 varied adjustment. 



The plumb bob e (Figs, la, 2a) is a loaded pivoted cylinder 

 with peripheral graduations for about 110 deg. and it 

 oscillates in consonance with any variations in the inclina- 

 tion of the inner and outer casings a and b. Its graduations 

 can be read through a casing cover glass o (Fig. 2a), which 

 carries a zero mark. The spring-operated means for 

 clamping this plumb bob are the clamping levers p,p, which, 

 when in action, bear on the plumb bob, retaining it in the 

 position it assumes at the point to be surveyed. This 

 clamping of the bob takes place through the cam plate q 

 (Figs, la, 2a, 4, 6). This clamping device permits of adjust- 

 ment of the plumb bob and compass at any of the three 

 positions a to c above. 



Between the plumb bob e and the bottom pivot in the 

 inner casing b is the other recording element, the compass 

 / (Figs, la, 2a, 8). Its box is pivoted at right angles to the 

 casing end pivots. Its clamping device is the bell-crank 

 lever s engaging cam plate q. This lever projects to hold a 

 spring t actuating the releasing and retaining lever u 

 keeping lever s engaged in cam plate q and thus, by further 

 leverage, engaging the compass box e about and below. 

 The compass box is suitably borne and loose bushed for 

 leverage clamping by means of springs working in grooves 

 from the levers, as seen in Figs. 7 and 8. Cam plate q is 

 fixed in its position by a pin v before insertion into the 

 borehole and on its removal allows the necessary initial 

 engagements to be made. In the position shown in Figs, 

 la, 2a, and 4, cam q and its cooperating parts are set by pin 

 V. The clock is now set so that after a predetermined time 

 the end of releasing lever u will be engaged. This releases 

 lever u, the plumb bob and compass being both free (Fig. 8) 

 with the compass needle clamped by a spring x. In this 



