134 THE VOYAGE OF H.M.S. CHALLENGER. 



sprinkling of hoar-frost, too slight to give any serious check to vegetation. The thermometer 

 daring summer rarely ascends beyond 74° in the shade, and stands at about 110° when exposed 

 to the meridian sun. At night it occasionally falls as low as 48° or 50°. 



" If we may give credit to the information of a man of the name of Currie, who has lived 

 on the island for the last six years, its climate may be regarded as one of the most rainy in 

 the world. According to his account, the months of January, February, and March are the 

 ouly period throughout the year in which fair weather may be expected with any degree of 

 certainty. During the other nine months the rain, he told us, is almost perpetual. How far 

 the latter part of this statement may be correct remains still to be proved ; but it was our 

 misfortune so far to experience the fallacy of the first, that from the 28th of November, the 

 day on which the detachment landed, to the 30th of March, when I quitted the island, it rained 

 on an average every second day. 



"This excessive humidity is not, however, entirely chargeable to the latitude in which the 

 island is situated. Of this we had frequent and tantalising proofs ; for, at the very time that 

 the rain poured heaviest down, we could plainly distinguish, from under the skirts of the cloud 

 which hung over, the distant horizon illuminated by the rays of the sun. 



" The power which high mountains possess of condensing the moisture of the atmosphere and 

 precipitating it in the form of rain is nowhere, indeed, more apparent or more unremittingly 

 exerted than on this island. The upper region of the mountain is usually involved in a thick 

 cloud, which not only obscures the whole island, but extends its shade to some distance over 

 the surrounding ocean. From this cloud the rain descends in heavy and protracted showers, 

 for the most part on the lower ground only, but occasionally on the summit also. In the latter 

 case its fall is announced by the sudden appearance of torrents of water pouring in a hundred 

 channels over the edge of the precipice, dashing down from cliff to cliff, and forming a series 

 of cascades the most magnificent, perhaps, on the whole face of the globe. 



"With such a moist climate and such frequent rains, it is a circumstance worthy of remark, 

 that the island is but scantily supplied with running water. The only permanent stream of any 

 magnitude in the whole island is one which gushes out at the base of the mountain immediately 

 behind the cantonment. Excepting this brook, you meet with nothing from one end of the plain 

 to the other but the dry beds of mountain torrents, which are impetuous, indeed, while they flow, 

 but cease with the shower to which they owe their existence. 



" The prevailing winds off Tristan da Cunha blow from the westward and southward. Strong 

 gales are frequent, but rarely continue above twenty-four hours. They never blow quite home on 

 the islands, but incline upwards at some distance from the shore, and striking against the face of 

 the mountain, are beat back on the low land in furious whirlwinds." 



Mr Moseley experienced one of these gales, which he describes 1 in the following 

 words : — 



" I botanised under the cliffs on the lowland in the morning, and intended to reserve the upper 

 plateau and cliff ascent for the afternoon ; but, as I was making my way up the steep slope above 

 the settlement in the afternoon, at about three or four o'clock, suddenly a dark squall came scudding 

 over the sea, and rapidly reaching us, chilled us to the bone. My guide, a small boy, born and 

 bred in the island, crouched down instantly under the tall grass and fern, lying on his side, drawing 



1 Notes by a Naturalist on the Challenger, p. 112. 



