AGASSIZ : BERMUDAS. 225 



Darwin's suggestion that the fringing reef on the south side of the 

 Bermudas is evidence of recent elevation, does not, in view of the fact 

 that the reef is made np of aeolian ledges, need any discussion. Nor is 

 the reason given by Dana regarding the cause of the great difference 

 in the amount of dry land on the north and south side of the atoll a 

 satisfactory one, if the ledges are a^olian ledges, which were the hrst to 

 disappear after subsidence began. 1 am inclined to look npon the 

 present state of things as due to the former existence of lower teolian 

 hills on the northern edge of the islands ; ^ but his views would apply 

 for proto-Bermudian times. 



My oljservations lead me to look npon the beach rock of the Bermndas 

 as consisting mainly of the larger and heavier seolian materials, which 

 either have not been carried so far or blown to so great a height as the 

 li'-hter wolian sand. The effect of the intermittent submersion of the 

 seolian rocks exposed at low-wate • mark seems to be to cement the par- 

 ticles on the exposed liui;.s of thj knife-edged strata by a process very 

 similar to that going on ni all the dee[) road cuts on the islands. By it 

 all traces of stratitication arc grad lally lost, and an upper crust running 

 over the exposed surface is foni ed irrespective of the a^olian layers. 

 Thus a belt of comparatively hard rock is formed, covered with a crust 

 ringiug to the hannner, which at first sight appears to be imconformable 

 ■with the teolian strata. A closer examination invariably reveals at no 

 great distance traces of the continnation of the aiolian stratification, 

 which contimie plainly visil)]e to high-water mark, to points below it, 

 and at intermediate heights. "Where the sea bi-eaks violently against a 

 vertical cliff, this cementing effect, accompanied by the disappearance of 

 the evidence of stratification, c;in be traced in some cases well above 

 high-water mark, whei-e it giadually jiasses into the region honeycombed 

 and pitted by the action of the rains. Snch parts of the rocks cannot 

 be distinguished from the base rock, and they have all its characteristics 

 except that the cementation is not rpiite so complete (Plates XV. -XVII. 

 and X.VVIII.). 



Here and there alnng tlie beaches beach rock is forming, as in some 

 parts of (ireat Turtle B;iy, of the shore south of "Whale Bay, in Whale 

 Bay itself, and lietween short pi-ojectinu' headlands where the (h'hrix from 

 the outer and inner ledizcs accunndates in greater quantity. This beach 



^ It «eems somewhat Iinznnlou'; to Mtt(>nijit, ns T\ice lins done, to correlate tlie 

 movcmontA of elev;iti')n ami subsidence of what proliah'y is a volcanic cone — of 

 which lie lias, as he thinks, foiiinl evidence — with iliose of the iVmerican conti- 

 nent. (Rnll. Nat. Mus., No. 25, p 18 ) 



VOT, XXVT. XO. 2. If, 



