Variation of Hourly Meteorological Normals at Kimbcrley. 171 



normal minimum also comes at the same time, it follows that the 

 depression here simply exaggerates the normal conditions of pres- 

 sure. The downward tendency of the barometer during the 

 mornings of the day before and of the day itself causes the princi- 

 pal maximum of pressure to come fully half an hour earlier, namely, 

 from 9 a.m. to 8.30 a.m., and in the same way retards it to 9.30 a.m. 

 on account of the upward tendency during the day after. Also the 

 secondary maximum, occurring normally at 11 p.m., comes an hour 

 earlier on the first day, and perhaps an hour later both on the day 

 and the day after. In the same way the afternoon minimum of 

 pressure comes later on the first day and earlier on the third. The 

 greatest variation is shown by the morning minimum of pressure. 

 It comes half an hour later on the first day, nearly an hour later 

 on the second, and becomes practically abortive on the third, show- 

 ing itself, indeed, more as a retarded rise than an actual fall. The 

 deviations of pressure increase from appreciably zero to about one- 

 seventh of an inch in 40 hours, decreasing to zero again in the 

 remaining 32 hours. The double amplitude in the average depression 

 lasting three days is '21 inch — that is, *12 inch greater than the 

 double amplitude of the ordinary diurnal oscillation ; the double 

 amplitude on the day in which the centre passes over is actually 

 only "02 inch greater than the normal. 



The mean temperature of the first day is between one and two 

 degrees higher than the normal ; on the second day it is on the 

 whole about half a degree higher still ; while on the third day it is 

 between three and four degrees lower than the normal. According 

 to the hourly means of Table 4 the first day opens with a tem- 

 perature slightly higher than the normal ; there is then a gradual 

 positively-increasing deviation throughout the day until sunset ; for 

 a few hours during the evening the temperature is falling rather 

 more rapidly than is usually the case ; but by sunrise of the second 

 day the positive deviation is as large as before. There are signs of 

 three maxima in the positive deviation of temperature on the second 

 day, i.e., just after sunrise, at noon, and just after sunset. How far 

 they arise simply from the shortness of the record it is hard to say. 

 Certainly the drop at 3 p.m. on the first day can scarcely be other 

 than fortuitous. * After sunset of the second day the fall of tem- 

 perature is rapid, a zero deviation being reached at midnight. From 

 midnight onwards the negative deviation increases until it reaches 

 nearly —6° at noon. During the succeeding afternoon this slackens 



* A reference to Table 8 will discover a pronounced maximum in the frequency of 

 rain at this time. A more extended record would probably to some extent smooth. 

 out this asperity as well as that of temperature. 



