Buffington, Hamilton, and Moore 



This particular geometry obtains at all times when the submer- 

 sible is parallel to the sea floor and an accurate slope is being mea- 

 sured. If the submersible is down by the stern, the light will separ- 

 ate as shown in Fig. 2. 



Ill 1 1 1 1 nil nil III 1 1 



SEA FLOOR 



Fig. 2 - Lateral Aspect. The plane of the submersible is inclined 

 to the sea floor stern down. Resting on its "haunches," the maxi- 

 mum absolute separation of the lights is about 7°. This situation 

 obtains regardless of the sea floor slope. The only change is 

 angular rotation of the entire relationship with regard to absolute 

 horizontality . 



Correspondingly, if the bow is down, the lights again separate, 

 (Fig. 3) reversing their proximity to the observer's window. 



Close study of the geometrical relations between the submersible 

 and the sea floor in various situations will show that to guarantee par- 

 allelism between the horizontal plane of the submersible and the hor- 

 izontal plane of the sea floor, it is necessary to control the thwart- 

 ships axis running through the center of the sphere in the horizontal 

 plane. This control can be achieved independently of any external 

 observation or reference by simply observing the pendulum or inclin- 

 ometer inside the sphere which is adjusted to measure deviations 

 from an axis running thwartships. 



In Fig. 4 we have an anomalous situation where the two spots 

 coincide on the sea floor and the thwartship axis is horizontal. Yet 



84 



