COLLECTION AND ANALYSIS OF DATA 



175 



In recording direction of movement the whalers used the eight cardinal and sub- 

 cardinal points of the compass, noting the numbers seen travelling in each direction. 

 As will be understood the numbers recorded are much higher than for positions : many 

 more whales are sighted than are killed, and movements of the same whales arc doubtless 

 recorded on several occasions. With these records, as with those for positions, a number 

 of forms have had to be rejected as inadequate or unintelligible. 



In analysing the data the total numbers for each direction and for each month of the 

 season were found. The directions for each month were then reduced from eight to four 

 by subtraction of those travelling in opposite directions, and thence from four to two 

 by finding the components along two lines at right angles to one another. A resultant 

 direction and number was then obtained by means of traverse tables. We are indebted 

 to Sub-Lieut. R. A. B.Ardley, R.N.R., and Lt.-Cmdr. J. M. Chaplin, R.N., for their 

 valuable assistance in obtaining these resultant values. The resultant directions are 

 shown in Figs. 3-6 (pp. 182-3, 188-9) ^y means of arrows, and the length of each arrow 

 represents the resultant number of whales travelling in this direction expressed as the 

 percentage of the total number recorded as moving. Records with long arrows thus 

 have greater validity than those with short arrows. Results for any one month are 

 evidently of little value if only a small number of whales was sighted, and if the numbers 

 travelling opposite ways are so evenly balanced that only a small percentage is found 

 moving in the resultant direction the record will also be unimportant. We have omitted 

 all monthly records in which the recorded number of moving whales falls below 50, and 

 we have also omitted those in which the resultant number is less than lo per cent, of 

 the total number moving. 



The numbers of whales for which directions were recorded are shown in Tables 

 V-VIII. The data from South Georgia cover eight seasons, 1923-4 to 1930-1, and 

 comprise observations on 55,210 Fin whales and 17,706 Blue whales. Those for the 

 South Shetlands, for 53,573 Fin whales and 10,761 Blue whales, were obtained during 



Table V 



Numbers of Fin whales on the South Georgia grounds 

 with recorded direction of movement 



