OCEAN TEMPERATURES 365 



short time interval from June 2 to June 15, 1911, and are therefore 

 appropriate for the application of the theory developed on pages 360- 

 362 for estimating surface currents from temperatures. 



The mean position during the three days, June 2, 3, and 12, was 

 Lat 30 N, Long. 14?6 W, and that during the three days, June 13, 

 14, and 15, was Lat. 24 N, Long. 17? 3 W. The distance between these 

 positions is 6.74, the unit being a degree of latitude, and the mean 

 surface temperatures were respectively 18? 32 and 19? 12, each value 

 being the average of eighteen observations. In equation (73), page 

 361, (z 2 ) is the distance, measured in degrees of latitude in the 

 direction of the drift, and the initial position is in this case at Lat. 

 30 N. The direction of the drift was found to be to the south at an 

 angle of about 27 to the right (west) of the meridian, therefore the 

 change in latitude corresponding to the distance (z 2 ) along the 

 line of the flow is (cos 27) (z ) = .891 (z 2 ). From these 

 values and the numerical values of the constants given on page 346, 

 equation (73) becomes 



_ - .217(2 - Zn) 



= 22.6 (.891) (.41) (z z^+Be -- nl -- +(.891) (1.88JTJ 



which gives the temperature at any point along the stream line, the 

 mean velocity being H l degrees per month. 



To determine H t substitute the two mean temperatures with the 

 corresponding values of (z Z Q ), thus obtaining two equations 



18.32 = - 22.6 +"0 + 1.685J3' 1 

 and 



. 1.461 



19.12 = 22.6 + (.365) (6.74) + Oe~nT+ 1.685H, 

 Eliminating 6 gives the equation 



1.461 



-(4.28 + 1.6857IJ e~ST-\- 1.6S5H, = 5.94 

 from which the value of H lt found by trial is 



H l = 9.4 degrees per month = .78 miles per hour. 



Using this value of H l the theoretical temperature at any point along 

 the stream line is 



= 6.75 .365(2 * ) + 11.57e- 231< *~ fo) 



where (z 2 ) is negative since the latitude decreases in the down- 

 stream direction. 



