Eight times each day radio broadcasts giving locations or Umits of 

 all known ice in the North Atlantic were transmitted for the benefit 

 of shipping approaching the ice-patrol area. The different bergs, 

 if not again sighted or reported, were kept from five to seven days in 

 the broadcasts before they were dropped. 



The probable drift tracks of critical bergs were indicated when 

 possible. The surface isotherms were very successfully used to esti- 

 mate probable berg drift tracks and to determine limits of ice areas 

 to be searched. The isotherm curves were drawn partly from infor- 

 mation obtained by the ice-patrol vessels themselves, but mainly 

 from careful plotting and analysis of the surface water temperature 

 reports received by radio from cooperating vessels. The value of 

 these reports can not be overestimated, and it is hoped that their 

 number will increase annually. When every vessel crossing the ice- 

 patrol area, particularly those off the most usually traveled routes, 

 reports regularly to the patrol, then the latter will be able to render 

 the most efficient and useful service possible. 



Special messages were drafted and sent to any ship that inquired 

 for special information relative to ice, weather, routes, and similar 

 matters. The successive positions of vessels as plotted from their 

 water temperature reports were carefully watched. Whenever it was 

 apparent that a ship was following a course leading toward danger 

 the master was warned, safer courses or other suitable precautions 

 being suggested. Once each day a compilation of all ice sighted or 

 reported during the previous 24 hours was transmitted by radio direct 

 to the United States Hydrographic Office at Washington, D. C. 

 These reports were given wide dissemination among shipping circles 

 by the hydrographer of the United States Navy. 



The scientific work carried on b}^ the patrol in 1929 was similar to 

 that of previous years. Deep-sea soundings were obtained by the 

 echo method at frequent intervals for the purpose of improving the 

 bathymetrical charts of the ice-patrol area. Surface and subsurface 

 temperatures and salinities were determined at numerous oceano- 

 graphic stations. By the latter means it is possible to study the local 

 currents generated where the Labrador Current meets the Gulf 

 Stream, and to compare conditions prevailing in the different localities 

 cruised over with those that prevailed there during former months 

 and years. To facilitate reference and comparison the various sections 

 of this bulletin are on the same subject matters and have been arranged 

 in the same order as those in the 1928 Ice Patrol Bulletin, the 1928 

 publication itself being modeled on the form that has practically 

 become standard during recent years. 



