DAILY VARIATION OF TEMPERATURE. 



53 



to the large change of temperature which occurred between the beginning and 

 end of the month. The correction applied for this purpose is the usual one 

 + _,!_ (9- — f^^) (/i — 12) in which r^ and r.,^ are the mean readings answering 

 to the first and second midnights of the day and n the hour interval since the 

 first midnight. 

 (6) When the true daily variation of temperature has been obtained in this way, the 

 difference between the highest and lowest hourly values gives the daily amplitude 

 of temperature, 

 (c) The expression daily range of teviperature is strictly confined to the dift"erence between 

 the maximum and minimum temperatures recorded during each day. The average 

 value of the. daily range is much larger than the corresponding amplitude. 

 In the Antarctic the unperiodic temperature changes are so large in comparison with 

 those due to true period causes that a long series of years would be necessary to eliminate 

 them completely. By combining the results of the observations at Cape Evans and Hut 

 Point we have four years' observations for all the months from February to August and three 

 years' observations for the remaining months. In the following discussions the results of all 

 the years combined have been used and only where it is necessary in order to investigate 

 particular points will the results for individual years be separately considered. In the volume 

 of tables, however, the data for each year are given in such a way that they are easily 

 available for further investigation. 



The daily variation for each month is shown in table 20 and the results are plotted 

 in the left half of figure 20. As the data for Hut Point have been given only for two- 

 hourly intervals, it was only possible to combine alternate values of the Cape Evans' tempera- 

 tures with them. Hence two-hourlv intervals are used in the curves and tables . 



Table 20. 



Daily Variation of Temperature a.s determined from all the Observations of Captain Scott's first 



ami second Expeditions. 



