6 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
lems that present themselves after a more thoughtful consideration of 
the whole subject. 
Like so many of the problems that seem simple and easily disposed of 
at the outset, this one has turned out to be much less simple than was 
anticipated. And even now, after having worked at it for twenty-five 
years, I am more than ever impressed with the complexity, difficulty, 
and far-reaching nature of the problems surrounding these sandstone 
reefs. Above all, it seems evident that any satisfactory theory of these 
reefs must include the study of the geographic development of the coast- 
line, — a study not hitherto attempted. Certain theories that have been 
advanced in explanation of or in connection with these reefs are not 
discussed in the present paper because they are without the bases that 
would entitle them to serious consideration. One of these is the theory 
of their glacial origin." It has already been shown that there is no satis- 
factory evidence of glacial action in Brazil.” Another is the theory of 
the orographic relations of the reefs to the western Alps. This idea 
was suggested to Liais by the once famous but now almost forgotten 
Systemes de Montagnes of Élie de Beaumont.* 
The problems of the coral reefs have long been before the scientific 
world. І have not been able to undertake any comprehensive study of 
the coral reefs of Brazil, but I hope that this approaching of the subject 
from the geological and geographical side may throw some light upon 
these problems, so far at least as this particular coast is concerned. 
In discussing the coral reefs I have endeavored to weigh the evidence at 
my command and to reach logical conclusions unbiassed by any particular 
theory. 
There are several related topics which it was intended to discuss in 
connection with the ones here dealt with, such as the currents, winds, 
tides, submarine topography, and submarine erosion, but the paper is 
already too voluminous and those parts are omitted, 
A great desideratum in studying the history of the Brazilian coast is a 
good topographic map. This does not exist. The hydrographic charts 
are the only ones available, but these deal only with such features as 
interest navigators, while the maps of the interior are often little more 
than vague generalizations. It is cause for congratulation that several 
of the Brazilian states under the lead of Säo Paulo, whose survey is 
1 Nouvelle géographie universelle. Par Е. Reclus. Тоше XIX. Amérique 
du Sud, p. 222. Paris, 1894. 
2 The supposed glaciation of Brazil. By J.C. Branner, Journ. Geol. L, p. 753-772. 
з L'Espace Céleste. Par E. Liais, p. 544, 548. Comptes Rendus, 1860. L., 
p. 762-763. 
