[501] There are no observations for January, but since the mean relative humidity varies with the rainfall, I have approximately estimated that for January to be 83.
[502] Lieut. Lake’s observations for 1876 and 1877. (Quart. Journ. Met. Soc.)
The moderate intensity of the sun’s rays in these islands is to be ascribed to the presence of aqueous vapour in quantity in the atmosphere. When, however, a thunderstorm and its accompanying rain-squall are portending, the air is unusually dry, and the sun’s rays are very fierce. At such times it often happens that the sky is overcast; and thus it comes about that the unwary traveller, by rashly baring his legs and arms, suffers severe sun-burns when he least expects it. Waterton and other travellers have, through ignorance of this fact, been laid up for several days, and even weeks. I was unable to walk any distance for about ten days, after experiencing a severe sun-burn of the legs as the result of baring them during an overcast day. The affection is peculiarly painful, though it often excites but little sympathy.
My remarks on the meteorology of this group will not be complete without a short reference to the prevailing winds. The South-east Trade Wind and the North-west Monsoon carry on a continual struggle for the mastery in these islands. However, for two-thirds of the year the Trade prevails, viz., from April to November. The appended record of winds, which extends over a considerable period, I have prepared from the observations made on board H.M.S. “Lark” in different parts of the group, and from the registers kept by Mr. Sproul and Mr. Howard at Santa Anna and Ugi. It will be there seen that at the eastern extremity of these islands, viz., in the vicinity of St. Christoval, the Trade announces its onset in April by unsettled weather, and frequent thunderstorms. In May, it becomes established, but, as Lieutenant Leeper remarks, it blows in fits and starts, is interrupted by calms, variable winds, and heavy rain-squalls, and does not blow home as in Fiji and the groups to the eastward. At the opposite end of the group, in Bougainville Straits, the Trade appears a month later, and does not become established until June. In this locality, however, it is more fitful than in the eastern islands, blows lighter, and is less to be depended on by the navigator.
It may be generally stated that the north-west and west winds set in about the end of November or the beginning of December, and prevail until the end of March. Although heavy gales accompany the frequent shiftings of the wind, especially when it is from the S.W., these islands are beyond the sweep of the hurricanes which in this season of the year occasionally devastate the groups to the eastward. The period of the westerly winds in the Solomon Islands is also characterised by calms and variable winds. The exhilarating freshness of the Trade then gives place to the enervating influence of the Monsoon; and, in consequence, the period of westerly winds is the sickly season.
RAIN-REGISTER AT SANTA ANNA.
(Kept by Mr. Charles Sproul[503] between October 25th, 1882, and December 31st, 1883.)
[503] I am indebted to Mr. William Heughan for commencing this register.
The rain-gauge used was of the common round funnel pattern (5·7 inches). The observations were made at Port Mary on the west side of the island. The elevation of the guage was some four or five feet (or less) above the high tide level.