CORE ORIENTATION 85 



stationary and the pipe lifted from the attachment. Door 

 V permits access to the gyroscope compartment. The 

 direction of the core is read from the north indication 

 of the compass. 



The apparatus to be quite successful should have some 

 form of orientating coupling. The amount of inclination 

 being obtained directly from the core and frame dips, an 

 additional dip measurer for the barrel itself should be 

 provided to check the absolute core dip. This because a 

 fixed gimbaled gyrocompass is by no means as reliable in 

 dip readings as one slung from a buoyant ring in an annulus 

 of mercury. 



Dixon's Apparatus. — A. F. Dixon and D. Upham of New 

 York first invented this device in 1924,^ and it is essentially 

 a core orientating appliance. Its chief parts are a base 

 core-marking tool, an index sheet or card rotatable relative 

 to the tool holder, its position in azimuth controlled by a 

 gyrocompass, and a marking device for obtaining the sheet 

 position. 



Figures 1 and 2 (Plate V) are vertical sections of one form 

 of the device, it being noted that there are several possible 

 forms, according as the gyrocompass is in the apparatus 

 or a surface master gyrocompass is used connected down the 

 hole by wires to a ''repeater motor" lowered into the hole 

 with the index sheet, marking device and tool. Consider 

 the form of construction shown in Fig. 1 where we have a 

 bipartite cylindrical casing, the top part A of which is the 

 compass chamber and the bottom B is the tool holder 

 screwed on watertight. A cable w conducts current 

 to the gyroscopic compass C which is freely suspended 

 and carries a sheet or card S. Below S a marking device 

 M is mounted on top of chamber B and actuated by the 

 electromagnet E so that when the latter is momentarily 

 energized by a brief current impulse the marker is rocked 

 and pricks sheet S. The electromagnet circuit x may be 

 closed at will by switch sinB. The cable wires y supply 

 current to the B chamber electromotor P and can be 



1 U. S. Patent No. 1,130,694, May 31, 1927. 



