458 



Taking the year as a whole, we see a marked maximum frequency of occurrence between 10 p.m. and 

 2 a.m., the frequency being very nearly the same for the two hours before and the two hours after 

 midnight. There is a slight indication of a double period in the frequency, with a secondary maximum 

 near noon, the principal minimum occurring between 2 and 4 p.m. The number of occurrences of minimum 

 in the 12 hours ending at 8 a.m. bears to the number in the 12 hours ending 8 p.m. the ratio of 8 : 3. 



In the three midsummer months as a whole the occurrences between 8 a.m. and 8 p.m. form only 10 per 

 cent, of the total number, and in no single occasion did the minimum occur between 2 and 4 p.m. 



In the equinoctial season the occurrences between 8 a.m. and 8 p.m. rise to 30 per cent, of the whole, 

 and a minimum appears between 8 and 10 a.m., which differs but little from the principal minimum 

 between 2 and 4 p.m. While at midsummer only 28 per cent, of the minima occur in the afternoon, 

 in the equinoctial season the afternoon occurrences are slightly more numerous than the forenoon 

 occurrences. 



Coming to midwinter, we find a most interesting and well-marked diurnal inequality in the frequency 

 of occurrences. As at other seasons, the frequency of incidence between 10 p.m. and 2 a.m. is notably in 

 excess of that at other hours. But there is a well marked secondary maximum of frequency from noon 

 to 2 p.m., and the forenoon minimum is unmistakably the principal one of the day. Each of the 

 midwinter months shows the double period very clearly. The phenomenon is perhaps the strongest 

 evidence yet advanced that temperature in the Antarctic night is affected by decided diurnal and semi- 

 diurnal influences. 



6. The maximum thermometer being read and reset only twice a day at 8 a.m. and 8 p.m. 

 information as to maximum temperatures is much less extensive than that as to minimum temperatures, 

 and it is affected in addition by several uncertainties. If the highest temperature of a particular day, say 

 day n, occurred between 8 a.m. and 8 p.m , then it is given by the corresponding 8 p.m. reading of the 

 maximum thermometer ; but if it occurred before 8 a.m. or after 8 p.m. it may not be recorded at all. If 



TABLE VII. Means of Daily Maxima and Minima and of Daily Ranges. 



it occurred before 8 a.m. it will be given by the 8 a.m. reading only if it exceeds the highest temperature 

 occurring between 8 p.m. and midnight on day n-l. If it occurred after 8 p.m. it will be given by the 

 8 a.m. reading on day n + 1 only if no higher temperature occurred on that day before 8 a.m. One can 

 be absolutely certain of having the true maximum reading for day n only when the 8 p.m. reading on 

 that day exceeds the 8 a.m. readings both on day n and day n + l. In summer this was generally the 



