148 



Couthouy on Coral Formations 



vature of the hills to the south, and sometimes almost skirting 

 them at from the fourth of a mile to a mile from the shore. 

 The figure below represents a north and south section of the 

 plain, from just back of the ancient beach to the sea, on a 

 scale of 2.5 inches to a mile, and 10 feet to the inch. 



a. Surface soil, twelve to fourteen inches deep below the old beach, and 

 eighteen to twentysix inches deep above it. 



h. A decomposed lava ten or twelve feet thick, gradually passing into the 

 solid rock. 



c. A mixture of decomposed lava, surface mould, and coral and shell detritua. 



d. Ancient beach of coral rubble, shells, and volcanic earth and sand. 



c. A stratum of like materials with c. ten inches thick at its commencement, 

 but gradually attenuating as it approaches the sea till at one-fourth of a mile 

 from it, it is lost. 



/. A stratum of fine volcanic sand, chiefly comminuted crystals of olivine, 

 and fine coral detritus and shells. 



g. Thin laminae, the planes of whose stratification are parallel, formed by a 

 concretion of the materials of /. and having thin layers of locjse sand interposed. 



h. Present beach — coral rubble, shells and sand, chiefly coral detritus. 



These laminae were evidently formed by successive hori- 

 zontal depositions, but have since been tilted up so as to dip 

 about 5*^ north to the sea. Proceeding inland, after passing 

 the line of old beach, the surface soil is twice the thickness 

 of that on the seaward portion of the plain, and rests on the 

 stratum of decomposed lava. The layer of mixed earth, sand 

 and shells, was no doubt washed from the stratum at the time 

 when the sea was at the old beach. The bed of sand and 

 detritus on which this mixed layer, and after its disappearance, 

 the surface mould rests, is full of slight inequalities, as if rip- 

 pled up by the wind or sea. Probably the former was the 

 real agent after its elevation. In the opinion of several intel- 

 ligent residents, this plain has been formed merely by long 

 continued additions to the beach, but there are several facts 

 contradictory of this. 



