IV.
 
               The inner defenses of the canal
 
     1. The inner patrol. An inner patrol is now being con-
ducted by medium range bombers and flying boats on a radius of
400 nautical miles out from Panama. The main purpose of this patrol 
is to supplement the recognized gaps in our present outer patrol and 
to try to catch a carrier which has evaded that outer patrol. Its 
range, however, would afford no certainty of catching a carrier before 
she had released her bombers.
 
     On the Atlantic side a similar but less thorough 
short range patrol is also being conducted.
 
     2. The airplane warning service. A number of both fixed 
and mobile detectors (called by the Navy RADAR) are now in operation 
at various points on the coast including Salinas. Their principal 
mission is to detect the approach of a hostile plane. At present this 
mission, is being carried out ineffectively, partly on account of great 
geographical difficulties (causing confusing echoes) and partly because 
these American detectors are not effective in catching the approach of
a low flying  plane.
 
     A few weeks ago I sent a British expert, Mr. Watson Watt 
together with some Canadian assistants to Panama to examine this service 
and also to locate the proper places for some Canadian CHL detectors 
which I had the promise of from the Canadian government. These CHL 
detectors are effective on low flying as well as high flying planes. 
These CHL's are now on the way to Panama and sites have already been 
selected and they will all probably be in operation before the end of 
April. These foreign experts have also given us useful assistance in 
relocating and improving our original American instruments.
 
          Note: One of the mistakes of our original location was 
          in placing the detector on too high a base, it having 
          been discovered that such a height produced confusing
          echoes which prevented proper detection, when still higher 
          mountains lay behind the site.
 
     By these various steps the air warning service can be 
expected to be very considerably improved in detecting the approach of
low flying hostile planes. Our force of interceptor planes must be
enlarged.