308 THE CLIJiIATE OF LOUKIiXCO MARQUES. 



been registered whenever the temperature exceeded 32'' C. 

 (89.6= F.). 



This wind is unquestionably unpleasant. It is extremely 

 dry, and causes an impression not less disagreeable than the hot 

 damp winds. 



Barometric Pressure. 



Barometric Pressure, which plays an important part in 

 meteorology, is of secondary importance in the study of a climate 

 and its consequent influence upon human life, especially if we do 

 not consider its efTects upon the other elements, as its oscillations 

 seem to have a perceptible influence upon the human body, and 

 only in very high altitudes does it become a climatic factor of 

 importance. 



In Table No. V the monthly and annual means of the pres- 

 sure are shown for a period of seven years, reduced to 0° C. at 

 sea-level. 



Besides the double diurnal variation, improperly called 

 " tides," which are more or less satisfactorily accounted for bv 

 various theories, the annual variation taking place is well dehned. 

 The minimum in December and the maximum in July, and the 

 annual means, correspond to the April means, for the same 

 ])eriod of seven years. 



These annual variations occur in the opposite direction to the 

 variations of temperature, as is usual in temperate continents. 



if we analyse the variations in 24 hours we notice that the 

 nocturnal minimum generally occurs from III to IV, while the 

 diurnal minimum takes place, as a rule, between XV and X\'i, 

 while the morning maximum is registered between V'lII and IX. 

 with a tendency to occur earlier from October to December; the 

 nocturnal maximum is late, usually occurring between XXII 1 

 and XXI\\ and even after midnight. The diurnal minimum is 

 about 1 .5""" ( 0.050/') lower than the nocturnal minimum, thi::^ 

 being more i)ronounced from October to January ; the diurnal 

 maximum exceeds the nocturnal by about 0.5""" (0.0197"), the 

 higher difference taking place from June to October ; conse- 

 quentlv, the difference between the diurnal maxima and minima 

 is more pronounced than is the case at night. Most of these facts 

 seem to be explained by the daily march of temperature, as men- 

 tioned before, and to be connected with the hours of sunrise and 

 sunset. 



The extreme pressures as registered at the Observatory are : 

 :\Iaxinuun, 779.4""" (30.686"); minimum, 746.2™" (29.378"); 

 I.e., an absolute variation of 33.2'''"' (1.308"), which is within the 

 limits registered at Durban and East London. The absolute 

 minima naturallv correspond to the occurrence of depressions, 

 and are followed' by the maxima, which become more pronounced 

 when the anticyclonic system becomes more stably fixed upon the 



plateau. 



Besides these two reo-ular variations, daily and annual, one 



