232 DISTRIBUTION OF PLANTS. 



walking along the coral shelf, I observed cracks in it, continuous for 

 hundreds of feet, and only a little more irregular than the ice-cracks 

 of a frozen lake ; equally devoid of displacement of level, or geological 

 f\iult. Along the outer margin, were natural bridges, also holes in 

 the coral-shelf thirty or forty feet from the sea, but freely communi- 

 cating beneath ; and it occurred to me, that in such situations, a heavy 

 storm-wave might sometimes burst up portions of the coral-shelf, 

 throwing over fragments tons in weight, such as are often seen on 

 coral-islands.* 



The vegetable growth, as far as examined by myself, proved entirely 

 the same as on Taiara coral-island; but with less variety, nearly one- 

 half of the species being absent. An additional species was however 

 discovered by Mr. Brackenridge : 



Gen. Scirpoid (No. 1). Cespitose, three to four inches high; somewhat Dichroma-Iike, 

 except that the floral leaves are small and short, not enlarged, nor exceeding the ter- 

 minal cluster of spikelets. Found by Mr. Brackenridge. 



10. Ahii coral-island. In plain sight from Manhii, but much 

 smaller; seeming only " five or six miles in length and breadth," with 

 the lagoon destitute of an outlet. 



On the 7th, I landed with others, and remained several hours on 

 shore. The rim of land-surface measured " 2860 feet" across, or more 

 than half a mile ; and being wider than usual, the woods in some 

 spots were slightly forest-like; the Aclujranthes again constituting the 

 prevalent undergrowth, but here very luxuriant, suffruticose or 

 shrubby, and four to six feet high. 



* In further illustration of this subject, the following Newspaper extracts may be 

 compared : 



" A block of granite on Boon Island, about fourteen feet in extreme length, ten feet 

 wide, and from five to six feet in height, was lifted from its bed in the ledge, and carried 

 up an inclined plane of from twelve to fifteen degrees, to a distance of near sixty feet. 

 This occurred during a N. E. snow-storm, in the year 1852, and shows the power of 

 wind and waves." — (Portland Argus.) 



" Near Plymouth, England, during a heavy gale, a block of limestone, weighing seven 

 tons, was driven up by the waves to the distance of one hundred and fifty feet ; and 

 blocks of from two to three tons' weight Were washed about like pebbles. — It has been 

 found, by experiments made on the coast of Scotland, that the waves from the Atlantic fall 

 with twice the force of those from the North Sea. An Atlantic breaker will frequently 

 fall with a force of three tons to the square foot, or twenty-seven tons to the square yard.' 

 — (Reprint from an English Newspaper.) 



