was nade available for tests. This instrument employed the 

 saturated core magnetometer developed by Vacquier, Modifica- 

 tions and improvement of this instrument resulted in the 

 development of MAD Mark I, 



Although usable signals could be obtained from S-type 

 submarines , "the operation of MAD Mark I was not entirely 

 satisfactory,, The chief trouble lay in the fact that since 

 the detecting coil was stabilized by means of a gyroscope, the 

 fluctuations caused when the plane banked in going around a 

 curve were such as to obscure almost completely the minute 

 changes in magnetic intensity. It was realized that a far 

 more satisfactory method of orienting the coil v/ould be to 

 use the earth's magnetic field itself. 



Despite its deficiencies , the Mark I MAD was installed 

 in Navy blimp K-3 and saw service use, Meanwhile, of course, 

 the development work continued and MAD Mark II was produced 

 by the Gulf Company, A total of 14 Mark II units was pro- 

 duced and placed in service. 



Experimentation looking to the development of methods 

 for using the magnetic field alone to control the stabiliza- 

 tion of the magnetometer were undertaken by several of 

 Division 6»s contractors. The Bell Telephone Laboratories 

 succeeded in producing a magnetically oriented instrument 

 using saturated core magnetometers of the second harmonic 

 type o 



Meanwhile, the Airborne Instruments Laboratory of Divi- 

 sion 6, operating under a Columbia University contract,. was 

 not only conducting experimental work of its own a but also did 

 the testing for other groups engaged on the pro _ ..err. of mag- 

 netic detection. Laboratory staff members accumulated a total 

 of more than 9600 flight hours. They were present during 

 numerous bombing attacks on submerged targets, witnessed sev- 

 eral torpedoings and rescues, and acted as technicians on 

 the blimps and planes in which MAD apparatus was installed. 



The ultimate result of this work was the development of 

 the MAD Mark IV, Mark IV B-l and Mark IV B-2 systems and the 

 eventual production model AN/ASQ-1, and an experimental model, 

 AN/ASQ-2, Development of the BTL instrument, later known as 

 the Mark X, was continued under NDRC direction to the stage 

 of field tests upon a working model. After further development 

 under direction of the Naval Ordnance Laboratory, approximately 

 50 Mark X units were produced by the Western Electric Company 

 under a Navy contract. 



89 



