XVI 



INTRODUCTION. 



The great peculiarity of the climate is its moisture. It may truly 

 be said that there is not a day without some deposition in the form 

 of either fog, mist, rain, snow, or sleet. The diurnal oscillations of 

 the barometer were found to be -175; its extreme variation 1-420 

 in., its mean standing being 29 '545 in. At the time of the autumnal 

 equinox of the southern hemisphere, the oscillations of the barometric 

 column reached '638 above its mean standing. The climate is not a 

 cold one : the temperature during the latter part of our stay was pro- 

 bably not far from the mean annual temperature, viz., 46'7, and 

 its mildness may be accounted for by the quantity of moisture which 

 exists : the mean degree of moisture we found to be '907. The daily 

 range of the thermometer is small, seldom more than 10. The sun 

 exerts little influence, the sky even in the finest days being for the 

 most part overcast. The temperature shown by the thermometer 

 freely exposed to the sun gives a difference of 7 Fahr. The mean 

 temperature of the water was 48'7. This would indicate a higher 

 mean than the air; but it must be recollected there are influences 

 existing beyond the limits of this locality, in the form of currents, 

 which may bring the warmer or colder waters within the bays of 

 Tierra del Fuego : such is probably the case. It will be seen by 

 the diagram on Plate V., page 126, that the water maintained a 

 higher temperature than the air, although it had a gradual decrease 

 of 9 Fahr. as the season advanced. The prevailing winds were 

 from the southwest : we had thirty-four days from that quarter, four 

 and a half from the northward and westward, four and a half from 

 the northward and eastward, and one and a half from the north. 

 Nothing can afford a stronger evidence of the nature of the cli- 

 mate, than the fact of six gales of wind having occurred within 

 the space of twenty days ; they were all of extreme violence, though 

 differing in duration, the shortest being but nine hours, whilst the 

 longest was more than twice that time. On Plate V. there is a small 

 diagram of the movement of the barometer during these gales, veri- 

 fying the remarkable fact before mentioned, that a rise of the column 

 is coincident with the beginning of a gale ; and it may be farther 

 remarked, that, so long as the mercury is descending, fine weather con- 

 tinues. The thermometer also seems in some measure to indicate the 

 coming gales by a sudden fall ; this, however, may be owing in part to 

 the change in the dew-point, which was observed to fall previous to 

 these occurrences, showing greater evaporation and consequent cold. 



