1835. 



SQUALLS OVER LOW ISLANDS. 



507 



and so far as I have heard or observed, it is usually the case 

 that on land, a wide tract of flat country, without hills, or at 

 sea, a considerable space of partly-covered ground, nowhere 

 rising much above high- water, is subject to more frequent 

 and violent blasts of wind than mountainous or even hilly 

 regions, whether continental or island. 



Clouds are certainly attracted, even if their formation be not 

 hastened, by land ; especially when it is covered by trees : and 

 as low islands (such as those of the Dangerous Archipelago, 

 between 14° and 20° south) have no hill or height of any kind, 

 about which clouds attracted by the archipelago (taken toge- 

 ther) can gather and discharge a portion of their contents, 

 electrical as well as fluid, it may, I think, be inferred, that 

 the want of such a conductor as would be furnished by a 

 mountain five or six thousand feet high, is the reason why 

 clouds in various electrical conditions unite or oppose one ano- 

 ther, as the case may be ; and, in consequence, cause rapid 

 changes in the atmosphere around them ; of which the effects 

 are seen in squalls (sometimes with heavy rain, sometimes 

 without), and even in whirlwinds. Where high land acts as a 

 conductor between the earth and certain portions of our atmo- 

 sphere, there may be a continual, though unperceived, electrical 

 action. In connection with this subject I would, if I were able, 

 consider the effects of rapidly varying temperature over land, 

 and comparatively uniform temperature over ocean during 

 twenty-four hours ; which latter fact I might suspect to be 

 one reason why the great Humboldt could not discover any 

 particular electrical action, as indicated by his electrometers, 

 while sailing from Europe to Brazil : although those same 

 instruments were far from inactive after he landed. But I feel 

 myself out of my depth, and will leave such speculations to 

 those who are qualified to indulge in them. * 



On the 13th, after having passed some anxious nights in 

 very squally weather, -f- we were gratified by seeing an islet 

 whose existence we had not suspected. Tairo is the name by 



* See note (a) at the end of this chapter, 

 t All the squalls were from the westward. 



