262 Dr. Mac Culloch on the 
Arr. ILI.  Oncertain Elevations of Land, connected with 
the Actions of Volcanoes. By J. Mac Currocn, M.D., 
F.R.8. Communicated by the Author. 
Tue geological readers of this Journal need not be reminded, 
that one of the great problems in their science is to determine 
the nature of the causes whence rocks, once existing beneath 
the depths of the sea, are now found elevated far above its 
level. For proofs of the fact itself, we need not have recourse 
-to the observations of Ulloa on the fossil shells found at eleva- 
tions of 14,000 feet in the Andes, as the whole surface of the 
earth presents appearances of the same nature. 
Two distinct theories have been suggested for the explanation 
of this fact, yet without necessarily involving all the other 
points which have divided the two leading bodies of geological 
partisans. By the one party it has been attributed to the sub- 
sidence of the sea; the rocks, with their organic contents, 
remaiaing in the places where they had been formed: by the 
other, it has been supposed that the land has itself moved, 
while the sea remained at rest. In the last party also, there 
are some who, like De Luc, view all these changes of the land 
as having arisen from its subsidence into caverns; others who, 
like Hutton, consider that the effects have been produced by 
an elevating subterranean force; and a third party, who admit 
of both these modes and causes of motion. 
It must not be imagined that the theory of the elevation of 
the land is limited either to that system, which is best known 
by the name of Dr. Hutton, or to himself. It was originally 
proposed by Antonio Lazzaro Moro, and it has had many sup- 
porters among persons who never heard of an Huttonian theory, 
Nor is it limited to those who assign an igneous origin to cer- 
tain rocks and certain changes; since it was the opinion of 
Saussure, than whom no one ever maintained more strenuously 
that theory which is called the aqueous or Neptunian. 
It is not my intention here to enter into a critical examination 
of these theories. But it will not be irrelevant to remark, 
that the hypothesis which presumes on a subsidence of the sea, 
