32 
ATOLLS. 
Ch. L 
difficulty can sand accumulate on a slope, which, 
in some cases, appears to exceed fifty-five degrees ? It 
must be observed, that I speak of slopes where sound- 
ings were obtained, and not of such cases, as that of 
Cardoo, where the nature of the bottom is unknown, 
and where its inclination must be nearly vertical. M. 
Elie de Beaumont 1 has argued, and there is no higher 
authority on this subject, from the inclination at which 
snow slides down in avalanches, that a bed of sand or 
mud cannot be formed at a greater angle than thirty 
degrees. Considering the number of soundings on 
sand, obtained round the Maldiva and Chagos atolls, 
which appear to indicate a greater angle, and the ex- 
treme abruptness of the sand-banks in the West Indies 
as will be mentioned in the Appendix, I must conclude 
that the adhesive property of wet sand counteracts its 
gravity, in a much greater ratio than has been allowed 
for by M. Elie de Beaumont. From the facility with 
which calcareous sand becomes agglutinated, it is not 
necessary to suppose that the bed of loose sand is thick. 
Capt. Beechey has observed, that the submarine 
slope is much less at the extremities of the more 
elongated atolls in the Low Archipelago, than at their 
sides ; in speaking of Ducie’s Island he says 2 the 
buttress, as it may be called, which ‘ has the most 
twenty-five fathoms, and then ends abruptly, like the first; and 
immediately beyond this there is no bottom with two hundred 
fathoms. 
1 Memoires pour servir a une description G6olog. de France, tome 
iv. p. 216. 
2 Beechey’s Voyage, 4to. ed. p. 44. 
