294 J, D. Dana on the Origin of Prairies. 
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various parts of the world; and he proposes briefly to state some 
of the facts in its favor which he has noticed. s, 
On arriving, in 1889, off the north side of the island of Tahiti, 
one of the first of the Pacific islands visited by the Exploring 
Expedition under Capt. Wilkes, it was a matter of much sur 
prise that the land, so famed for its tropical fertility and beauty, 
was bare of trees over the lower ten or fifteen hundred feet of 
its slopes, the forest trees being confined—the valleys excepted— 
on the ascent of one of the lofty summits of the island, and on 
other excursions, confirmed this inference. Over the bare slopes 
shere were no marshy areas; and there was positive prool 
the structure of the island, the dip of the rocks beneath bemg =F 
always seaward, and in the nature of the surface, that there 
never had been such areas; while on the upper slopes, where 
moisture was abundant, and the ground often boggy, trees were 
of luxuriant growt 
Similar facts were observed on other Pacific Islands. One of 
them, i of the Navigator group, “was covered through- 
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ay here be 
learned that 
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