Pressure and Temperature Results for the Great Plateau. 265 
2. Starting now in the height of summer, when the temperatures 
over the table-land are the greatest possible, we have at any instant 
the whole atmospheric envelope of the southern hemisphere expanded 
upwards, the tendency of which is to decrease the differences of 
pressure between upper and lower stations. But the air being 
expanded over the high land not simply in terms of its altitude, but 
according to its temperature, the excess of volume presses coastwards, 
counteracting more or less completely the processes that make for a 
minimum pressure-difference. 
3. During February pressures are rising generally in the southern 
hemisphere. Also the temperature is rising over the coast, but 
falling over the table-land: that is, the pressure surfaces are still 
rising over the coast, but have begun to sink over the interior. 
More of the inflow from the north, therefore, goes to the table-land 
stations than to. the coast. 
4. During March temperatures are falling generally, and pressures 
are rising, the surfaces of equal pressure are tending to sink. But 
the temperatures of the upper stations are falling very much faster 
than those of the coast, and hence a small excess of the still expanded 
air (it still being warmer than the mean) is pressing inwards. 
5. During April and May temperatures are falling most rapidly at 
inland and coast stations alike. The pressure surfaces are still of 
themselves tending to sink faster over the interior than over the 
coast, but now it would seem are lost in the maximum effect of the 
general inflow from the north. Ina lesser degree the same applies 
to June. There is some irregularity in the behaviour of the 
barometer at this season, which seems to be due to the barometric 
depression that annually (probably) spreads over the land for a fort- 
night or so towards the end of May. The general character of this 
depression will be best understood after reference to the daily 
numbers in Tables 5 and 17. 
6. In July the mean temperatures of the table-land cease falling, 
and, indeed, saving for the annual cold wave of the month—to be 
mentioned again presently—would be actually rising; as the maxi- 
mum temperatures are in spite of the cold wave. At the middle 
stations and on the coast, however, the fall continues both by night 
and by day. ‘That is, the pressure surfaces over the coast and the 
slopes are still sinking, while over the higher land they are sinking 
no longer. At this time also the general pressure over the southern 
parallels is practically stationary at its highest amount. So the 
crests of the stationary or ascending pressure surfaces are free to 
extend laterally, adding something to the coast pressures [see Table 
25] and deducting something from those of the interior. 
