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uplift after a rapid subsidence. The latter conclusion has 
very frequently been drawn, and yet it is without proof. 
The former supposition is, I believe, the more probable of the 
two, because as above pointed out, reef-formation is more 
favored by subsidence than by uplift; but it is of course 
possible that some members of a series of uplifted reef terraces 
were formed during pauses in subsidence, and others during 
pauses in a later elevation. 
The only means of distinguishing between these possibili- 
ties is found in the detailed structure of the reef limestones, 
and it is a difficult matter to make detailed observations 
where the outcrops are generally covered by rank vegetation. 
The important point here is to locate any observations as to 
structure with respect to the total mass of the uplifted reef, and 
_ also with respect to the foundation upon which the reef rests. 
It is an easy matter to infer the structures that ought to be 
produced in a reef formed by upgrowth during subsidence, 
and in a reef formed by outgrowth during a stationary period. 
It is also easy to infer the relation that will exist between 
a series of older reefs formed during pauses in subsidence, 
and a series of younger reefs formed at different levels during 
pauses in elevation. Indeed, inference as to these structures 
today far outruns observation. Still, it is desirable that such 
inferences should be carefully borne in mind as a means of 
guiding the observer to points where critical observations on 
structure may be made. Some diagrams appended below will 
make clear the chief points here to be considered. 
One of the reasons that makes me particularly desirous of 
securing observations on coral reefs in the Dutch East Indies 
is that, as far as I can learn, the movements of elevation 
and depression that they have suffered in recent geological 
times have been of greater amount, of more frequent occurrence, 
and of more rapid rate than those which characterize the 
islands of the open Pacific. The East Indies appear to bea 
region of modern geological disturbance, in which many move- 
ments of many kinds have repeatedly taken place. It may 
