Boreas (N) 98 74 71 70 60 40 59 59 67 80 82 96 850 Kaikias (NE) 41 46 65 94 101 55 79 79 77 91 48 30 819 Apheliotes (E) 34 37 52 58 63 48 51 51 52 58 34 31 576 Euros (SE) 37 37 45 41 54 45 62 62 52 45 39 34 534 Notus (S) 82 66 95 99 143 155 128 128 118 93 81 65 1245 Lips (SW) 112 77 81 79 118 170 135 135 133 108 119 131 1402 Zephyros (W) 180 177 155 125 107 137 125 125 108 131 169 194 1732 Skiron (NW) 160 162 183 154 98 94 105 105 113 138 148 163 1607 -------------------------------------------------------------------- [Illustration: FIG. 14. VELOCITY OF SUMMER AND WINTER WINDS IN METRES PER SECOND] THE SEA BREEZE When the weather has been clear and moderately warm for two or more days, and the winds are light and variable, there may occur on the third day a moderate wind from the east, known as the sea-breeze. This occurs during anticyclonic conditions. Preceding the sea-breeze, the winds are very light, there are no clouds, and the temperature rises rapidly during the forenoon. This heating is due to a slow dynamic compression as the air slowly descends and the surface air does not flow away. There is no cooling because there is no evaporation due to air movement. The absolute humidity is low, often less than ten grams per cubic metre. Cumulus clouds do not form because there is no uplift of the lower air and consequently no chance for condensation of whatever water vapor may be present. No thunder-heads form notwithstanding the heat. The heat, while dry, is nevertheless extremely trying to men and animals. Relief comes in the early hours of the afternoon by the arrival of the sea-breeze. The usual explanation of the origin of the sea-breeze is that the land being excessively warm, the air over a relatively cool ocean moves in to take the place of the warm and therefore lighter air, which it is assumed has risen. Unfortunately for this explanation, the air over the land has _not_ risen; but on the contrary is falling slowly. Again the sea-breeze does not begin at the place where the temperature contrast is greatest, namely, just inside the shore line; but comes in from the sea. Nor does the flow extend far inland, which would be the case if there were up-rising currents. The sea-breeze is very shallow, generally not extending upward more than 200 metres, and often not above 100 metres. It does not penetrate far inland, as a rule not more than 15 kilometres, 9 miles. The sea-breeze is probably caused by a slow descent of dry, warm air, on an incline sloping from northeast to southwest. As it reaches the surface it is twisted more to the right; that is, becomes an east wind. It carries inland with it some of the air over the ocean which is much cooler and heavily saturated. MUGGY DAYS