AMERICAN 
JOURNAL OF SCIENCE AND ARTS. 
[SECOND SERIES.} 
Arr. XIX.— On Changes of Level in the Pacific Ocean; by 
James D. Dana.* 
Evipences of change of level in the Pacific are to be locked 
for In the height or condition of the coral reef formations or de- 
Posits; in the character of the igneous rocks; and in the features 
of the surface, The points of evidence are as follows :— 
A. Evidences of elevation. 
l, Patches of coral reef, er deposits of shelis and sand from 
the reefs, above the level where they are at present forming 5 
€ coral reef-rock has been shown occasionally to increase by 
stowth of coral, to a height of four to six inches above low tide 
level when the tide is but three feet, and to twice this height 
with a tide of six feet. It may, therefore, be stated as a general 
fact that the limit to which coral may grow above ordinary low 
tide, 1s about one-sixth the height of the tide, though it seldom 
allains this height. 
P this arte 4c : : 
i8 a conti article, cited from a chapter in the author’s Expl Exp. Geological Report, 
829, ., sation of the previous depuis on the Pacifie Islands, xi, 857, xii, 25, 165, 
"pe 185, 338, and xiv, 76. 
Senirs, Vol. XV, No. 44.—March, 1853, 21 
