patrol ; and during light years or years when good aerial observing 

 conditions continue later than usual, the use of aircraft results in a 

 lower over-all cost for the season. 



COMMUNICATIONS 



The daily schedule of ice broadcasts to shipping was maintained 

 from 18 March to 15 June. Each broadcast was preceded by a general 

 call on 500 kilocycles after which the transmitting station (Radio 

 Argentia, NWP) announced the NIDK ice bulletin with the operat- 

 ing signal to shift to 480 and 8100 kilocycles. After shifting to these 

 frequencies there followed a 30 second period of test signals to permit 

 receiver tuning. The ice bulletin was then broadcast twice, the first 

 transmission being made at 15 words per minute and the second 

 transmission at 25 words per minute, with a two minute interval 

 between transmissions. Times and frequencies for the daily broad- 

 casts were as follows: 



These times of transmission were selected so that each bulletin 

 would contain the maximum amount of recently received informa- 

 tion, would be transmitted with the least number of breaks due to 

 silent periods, and would be completed during the hours when the 

 operators on single-operator ships were on duty. In addition, the 

 morning broadcast was timed to include a digest of the reports 

 which increase in number during the first few hours after daylight ; 

 and the evening broadcast was timed to include the results of any 

 aerial reconnaissance made during the day. 



Each bulletin followed the same general pattern. The most recent 

 ice information was given first, listing the ice from south to north 

 and east to west. As in previous years, a distinction was made be- 

 tween ice sighted by units of the International Ice Patrol, i.e., ice- 

 patrol aircraft, the oceanographic vessel, or one of the ice-patrol 

 vessels, and that sighted by all other units. The former was listed 

 as ice sighted and the latter as ice reported. 



Since there were no ice-patrol vessels on patrol in 1919, merchant 

 vessels were not requested to make four hourly reports while in the 

 ice-patrol area. However, some merchant ships did submit such re- 



