OF ARTS AND' SCIENCES : SEPTEMBER 11, 1866. 147 



tions are the plainest, and the regions of vegetation best defined, we 

 have an island whose shores are the lower slopes of three mountains, 

 the relative position of which is that of the three angles of a nearly- 

 equilateral triangle. These mountains enclose an extensive plateau at 

 an elevation of about 5,000 feet. The windward shores and slopes of 

 Hawaii are the most rainy part of the group, in consequence of the 

 high peaks above, which condense the moisture of the trade winds, 

 and keep it almost continually falling. The elevated plateau is dry, 

 as much on account of its sterility, as it is sterile on account of its dry- 

 ness ; for whatever rain reaches it sinks into the porous lava soil as 

 fast as it falls. The low region is comparatively sterile on account of 

 its being cut off by the high intervening peaks from the reach of the 

 trade winds, and its heat quickly evaporates any thin clouds which 

 may drift over it. The higher leeward regions possess of themselves 

 sufficient coolness to condense the moisture of the air into clouds ; and 

 it is owing to the protecting influence of the mountain peaks that the 

 clouds are not blown away by the strong trade winds before they de- 

 posit their moisture, as is the case in some places. Thus we have a 

 wet region all along the eastern side of the island, and extending 

 around to the south and to the west, until it reaches the base of 

 Hualalai; and this wet region, between the height of 1,500 or 2,000 

 feet to about 5,000 feet, is the most heavily wooded of the group. 

 The parts between 1,500 feet and the sea level comprise compara- 

 tively few species, and but little of the peculiar vegetation. The high 

 and dry mountain tracts, above 4,000 or 4,500 feet, are very distinct 

 in their character and vegetation from either of the regions below. 

 The highest lava summits are nearly destitute of vegetation. 



Similar considerations, making allowances for physical contour, &c, 

 explain the similar distribution of wet and dry regions, and of vege- 

 tation, on the other islands. Thus, the summit of Haleakala, above 

 6,000 feet, has the character and nearly the same plants as the higher 

 parts of Hawaii, and its windward slopes are wet and heavily wooded. 

 The high summit stands in the way of the winds in such a manner as 

 to make an eddy to the leeward, where clouds gather every day, and 

 supply sufficient moisture to sustain a forest, while other parts are more 

 frequently cloudless and drier. The summits of West Maui, Oahu, and 

 Kauai, lying between the heights of 4,000 and 6,500 feet, are just in 

 the cloud level, and, being also peaks where denudation has long been 

 active, the foil has become somewhat impervious to moisture, which 



