88 The American Geologist. Feb. i89o 
somewhat rapidly these two curves took the arrangement 
shown in fig. 3. The zone of greatest cooling is now below 
the surface but that surface is not cool 
enough to allow the curve of contraction to 
return to the axis. Consequently there 
w^as then no "layer of no strain." But 
at later date when the surface had grown so 
cool as to cease to give off 
any perceptible degree of 
heat the state of things repre- 
sented in fig. 4 ensued where 
the curve of contraction re- 
urns to the axis or so nearly 
to it that intersection takes place and the 
"layer of no strain" appears. 
From that time to the present this layer has 
descended lower and lower accompanying 
at a certain distance the level of greatest 
contraction and will continue to sink deeper 
and deeper until the cooling of the sphere is complete. 
THE ORIGIN OF THE PRESENT OUTLINES OF THE 
BERMUDAS. 
By J. Walter Fewkes, Boston, Mass. 
The Bermudas consist of a number of coral islands 
which exhibit curved and crescentic outlines. The 
"Main Land," the largest of these islands, presents a marked 
feature in the partial or complete enclosure of at least three 
basins of water called sounds, which are irregularly oval in 
outline and more or less completely surrounded by land. The 
preser>t islands are for the most part strung along in an 
extended arc of an oval which skirts the platform upon which 
they are situated. 
Two theories have been suggested to explain the position 
and contour of these islands, the existence of the sounds and 
their relation to the platform from which the lands rise. These 
theories may be known as the "subsidence theory" and the 
"erosion theory." The latter has also been called, not inap- 
propriately, the "cave theory," for reasons which will, it is 
hoped, appear as we go on. 
