156 



CLOUD AND PRECIPITATION. 



but it has been possible to interpolate the missing observations between 1st March, 1911, and 

 the end of October, 1912, so that the daily variation has been obtained for twenty months, 

 with a fair degree of accuracy. 



A casual glance at the results for individual months shows that one or even two years' 

 observations are quite insufficient for giving a true value of the variation. The data for the 

 individual months have, therefore, been given in the volume of tables, and we shall consider 

 here only the results obtained by combining the new data with those obtained at Hut 

 Point during the Discovery Expedition. Unfortunately in the discussion of the Discovery 

 results the monthly mean cloud amounts at the different hours are only given in whole 

 nunibsrs. As the daily variation in most months is of the order of one unit, this rounding 

 makes it impDssible to combine the results there given with the new series. It was therefore 

 necessary to recalculate the whole of the cloud data for the two years' observations at Hut 

 Point. These new values will also be found in the volume of tables. 



On the Discovery Expedition observations were taken at the even hours of local time, 

 therefore to combine the results with those of Cape Evans, which were taken at the odd 

 hours of local time, it has been necessary to take the mean value between the successive 

 observations at Hut Point. Thus the values for 7 a.m. local time at Cape Evans have been 

 combined with the mean values for 6 and 8 a.m. at Hut Point, and so on. 



The following table gives the departure from mean for the mouths and seasons based on 

 all the available data. 



Table 87. 



Daily variation of Clotid Amount [Hut Point and Cape Evans). 



