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APPENDIX. 
stratification are obscure, but in one spot there was an in- 
cluded layer of stalactitic limestone, an eighth of an inch in 
thickness. In another place some false strata, dipping 
landwards at an angle of 45°, were capped by a horizontal 
mass. On each side of the ridge quadrangular fragments 
have subsided ; and the whole mass is in some places 
fissured, apparently from the washing out of some soft 
underlying bed. One day, at low water, I walked a full 
mile along this singular, smooth, and narrow causeway, 
with water on both sides of me, and could see that for 
nearly a mile further south its form remained unaltered. 
In Baron Boussin’s beautiful chart of Pernambuco (Le 
Pilote du Bresil ) it is represented as stretching on, in an 
absolutely straight line, for several leagues ; how far its 
composition remains the same, I know not ; but from the 
accounts I received from intelligent native pilots, it seems 
to be replaced on some parts of the coast by true coral- 
reefs. 
The upper surface, though it must on a large scale be 
called smooth, yet presents, from unequal disintegration, 
numerous small irregularities. The larger embedded peb- 
bles stand out supported on short pedestals of sandstone. 
There are, also, many sinuous cavities, two or three inches 
in width and depth, and from six inches to two feet in 
length. The upper edges of these furrows sometimes 
slightly overhang their sides ; and they end abruptly with 
a rounded outline. A furrow occasionally branches into 
two arms, but generally they run nearly parallel to each 
other, in a line transverse to the sandstone ridge. I know 
not how to account for their origin except through the 
washing to and fro of pebbles in originally slight depres- 
sions, by the waves which break daily over the bar. Op- 
posed to this notion is the fact that some of these furrows 
were lined with numerous small living Actinia. The 
exterior surface of the bar is coated wuth a thin layer of 
