THE ATMOSPHERE AND ITS CURRENTS. 



451 



openings, where a cold north-west wind blows regularly during the nights of summer, so 

 that the inhabitants of the village of Bland can winnow their corn at no other time. 



7. Hurricanes. Sudden and tremendous bursts of storm are common in mountainous 

 districts, and in the plains which lie at the base of those vast piles of nature's building. 

 Their peaks, exposed by elevation to intense cold, and covered with perpetual snow, cool 

 and condense the warm air rising up from the regions below which descends with 

 an impetus proportioned to its own gravity and the lighter condition of the air over the 

 regions below, and a tempest ensues upon considerable condensation and rarefaction in 

 adjoining regions of the atmosphere. This is the origin of the pamperos, or south-west 

 winds, which rush from the snows of the Andes, and sweeping over the level pampas 

 with unchecked violence, become hiirrirnnes before their arrival at Buenos Ayres, and 



Hurricane in the Tropics. 



carry to the city clouds of dust collected from the plains, occasioning almost total darkness 

 in the streets. So sudden is the operation of the pampero, that persons bathing in the 

 river Plate have been drowned by the agitation of its waters through the tempest before 

 they could possibly reach the shore. Captain Fitzroy relates, when in his ship upon the 

 river, that a small boat had been hauled ashore above high-water mark, and fastened with 

 a strong rope to a large stone, but the pampero set in, and afterwards the boat was found 

 far from the beach, shattered to pieces, but still fast to the stone, which it had dragged 

 along. But this violent movement of the atmosphere is remarkably beneficial in its general 

 effect to the inhabitants of the pampas of Buenos Ayres and on the banks of the Plata. 

 The pi*evailing winds through a great part of the year are northerly, and these passing 

 over extensive marshy tracts bring with them a degree of humidity, which renders the 

 land rife with fever and pestilence, till the pampero rushes down from the Andes and 

 clears the atmosphere. A somewhat similar wind, is one of our own physical phenomena, 

 hitherto unexplained, to the violence of which the tourist to the Cumberland lakes may 

 occasionally be exposed in spring and autumn. This is the Helm-wind. Hutchinson, in 

 the history of the county, and the Rev. J. Watson, in a report to the British Association, 

 have given an account of its singular features. When not a breath of air is stirring, or a 

 cloud is to be seen, a line of clouds will be suddenly formed over the summits of the Jofty 

 ridge of mountains at Hartside, extending several miles on the western side. To this 

 collection of vapours the term Helm is applied from its shape. It exhibits an awful and 

 solemn appearance, spreading a gloom over the regions below, like the shadows of night. 

 Parallel to this, another line of clouds, called the Bar. begins to form. The two lines unite 



