30 



HAYES-DETECTION OF SUBMARINES. 



XANO WHe£L- 



DIAL POINTEI? 



-PlPt* TO 



•riTHOfcerc 



U»WM BCAtwia 



Plate VIII. a. One form of "C-Tube " developed at the Nahant Stat 



ion. 



Plate XL a. One form of Double M-F Tube. Portion of casing removed to 



show receiver units. 



