Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2- Appendix): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

314 APPENDIX. weather ; they increase graduall}% the weather changes, and at times they end in a determined heavy gale. More frequently they rise to the strength of a treble -reefed topsail breeze, then die away gradually, or shift to another quarter. From the north the wind always begins to blow moderately, but with thicker weather and more clouds than when from the eastward : it is generally accompanied by small rain. Increasing in strength, it draws to the westward gradually, and blows hard from between north and north-west, with heavy clouds, thick weather, and much rain. When the fury of the north-wester is expended, which varies from twelve to fifty hours, or even while it is blowing hard, the wind some- times shifts suddenly into the south-west quarter, blowing harder than before. This wind soon drives away the clouds, and in a few hours causes cleai- weather, though perhaps with heavy squalls pass- ing occasionally. In the south-west quarter the wind (generally speaking) hangs several days, blowing strong, but moderating towards the end, and admitting two or three days of fine weather. Northerly winds then usually begin again, during the summer months ; but all manner of shifts and changes are experienced, from north to south by the west, during that season ; which would hardly deserve the name of summer, were not the days so much longer, and the weather a Httle warmer. Rain and wind prevail during the long, much more than in the short days. It should be remembered that bad weather never comes on sud- denly from the eastward, neither does a south-west or southerly gale shift suddenly to the northward. South-west and southerly winds rise suddenly as well as violently, and must be well considered in choosing anchorages, or preparing for shifts of wind at sea. The most usual weather in these regions is a fresh wind between north-west and south-west, with a cloudy overcast sky. Much difference of opinion has prevailed as to the utHity of a barometer in these latitudes. I may remark, that during some years' careful trial of a barometer and sympiesometer (Adie's), I found their indications of the utmost value. Their variations did not of course correspond to those of middle latitudes, but they corres- ponded to those of high northern latitudes in a remarkable manner, (changing south for north, east and west remaining the same). Gales of wind from the southward, and squalls from the south-