vessel, once every four hours, their position, course, speed, sea-water 

 temperature, and weather conditions. These temperatures were 

 plotted on the water-temperature chart, from which the positions of 

 the "cold wall" and Arctic water areas were determined. It may 

 be of interest to note here that the "cold wall" is a name given to 

 the boundary between the Arctic and Gulf waters. There is a notice- 

 able difference between the temperature on either side of the cold 

 wall and also a distinct change in color, the Ai'ctic water being green 

 and the Gulf water being blue. Wlienever a vessel approached the 

 cold-water area to the southward the master was further requested 

 to submit the above information hourly, in order to secure sufficient 

 data to determine the v>ddth of the Arctic water area. The positions 

 of the ships were also plotted on the ship chart and track kept of all 

 the vessels in the area or approaching the same. The meteorological 

 data was plotted on the weather chart and certain of the reports 

 transmitted to the Weather Bureau at 8 a. m. and 8 p. m. (seventy- 

 fifth meridian time) daily. 



The ice and obstruction reports were plotted on the ice chart and 

 the set and drift calculated for further dissemination to the passing 

 vessels. The bergs were followed constantly until their disintegra- 

 tion was complete or until they drifted into an area not traversed 

 by passing ships and were no longer a menace to navigation. Daily 

 at 8 p. m. (seventy-fifth meridian time) the patrol vessel transmitted 

 a resume of the ice conditions on the Grand Banks to the 

 Hydrographic Office at Washington, D. C. 



During the season the patrol vessels based temporarily at Halifax, 

 obtaining their fuel and supplies at that port, and alternated every 

 15 days on patrol duty. 



The Canadian Government assigned a vessel to ice-patrol duty in 

 the waters from Cabot Strait inland to keep merchant shipping 

 advised as to the ice conditions in the Gulf of St. Lawrence and the 

 straits. This vessel cooperated constantly with the lampa and the 

 Modoc while on ice patrol duty. 



In addition to the patrol another precaution, that is followed the 

 year around, has been taken to protect the vessels passing in vicinity 

 of the Tail of the Grand Banks. Certain routes or tracks across the 

 North Atlantic Ocean have been established, known as the North 

 Atlantic lane routes. These routes lead to the important ports in the 

 northern part of the United States and those of Canada. There are 

 seven tracks, tracks A to G, inclusive. Each track covers the east- 

 bound and westbound traffic. The eastbound tracks are approxi- 

 mately 60 miles south of the westbound. The use of the individual 

 track is dependant on the destination of the vessel, the season of the 

 year, and the location of the ice. The list of the tracks is contained 

 72733—261 2 



