14 



of the patrol (se^ fig. 50, p. 90), during which time the waters of the 

 entire eastern side of the Grand Banks were mapped. This timely 

 information enabled the patrol to forward to Washington officials an 

 intelligent and accurate recommendation regarding the safety of the 

 trans-Atlantic tracks. The drift of the ice and the stream lines of 

 the currents, as calculated from the station data, agreed very closely. 

 The methods employed in determining the direction and velocity of 

 the currents around the Grand Bank, which are described in Bulletin 

 No. 14, 1925, appear very feasible and the results in 1927 certainly 

 threw an intelligent light upon the probable movements of the ice, a 

 subject which naturally is of inestimable value to those in charge of 

 the patrol work. 



The patrol ships had on board practically the same outfits as carried 

 in 1926 with the exception of a larger number of spare oceanographic 

 instruments. The installation of new electric hoists for lowering and 

 hoisting the water bottles was a great improvement which shortened 

 the time spent at stations by almost one-half. The policy begun 

 in 1926 of carrying out a survey of the bottom contour whenever 

 opportunity afforded was continued by the Tampa in 1927, and 

 about 435 sonic soundings were obtained in this manner. The sonic 

 apparatus is also of invaluable assistance in locating the position of 

 the patrol ships, and the ice sighted, during the protracted periods of 

 cloudy and foggy weather around the Banks. The radio apparatus 

 functioned quite satisfactorily this year with the exception of three 

 days when the Tampa's main motor radio generator developed a 

 ground. The trouble was located, however, and by working night 

 and day the patrol ship was soon back on radio schedules. The 

 breakdown, it should be added, did not affect the set which is used to 

 communicate with passing vessels, as the spark set is on a separate 

 generating circuit. 



About 450 steamships are known to have taken advantage of the 

 service provided by the ice patrol this year, and no doubt there were 

 many more, that also listened in for the daily broadcasts. We made 

 a few inquiries as to how far the ice patrol reports were picked up, 

 and what the general policy was among the steamers regarding 

 listening in for the ice broadcasts. The replies indicated that radio 

 contact with the patrol was usually made at a distance of about 450 

 miles east and west of the Grand Banks; also that the commercial 

 radio operators were given standing orders to copy the broadcasts at 

 all times when within this range, giving the messages priority over all 

 other traffic. The following list is submitted in order that the reader 

 may obtain an idea of the service which is being furnished the ships 

 of many nations. The masters of these vessels have been thanked, 

 by letter, by the chairman of the ice patrol board. 



