Fig. 18. View of potential-gradient recorder and eye-reading apparatus on stern rail of ship. 

 Note how the boom crutch dominates the location, and shields the apparatus from distortion of 

 the earth's field arising from the installation or removal of the quarter-deck awning. The 

 mainsail is up with boom to starboard, a position designated as MUBS in this volume 



Fig. 19. View of potential-gradient apparatus from quarter-deck with awning up. Note the small 

 boat on davits at the port rail, probably contributing somewhat to the distortion of the earth's 

 field at the stern of the ship 



27 



