112 ^Proceedings of the Royal Physical Society. 
The theory of a Central Heat, or of a High Tem- 
perature IN the Interior of the Earth. The hypothesis 
of a central heat is of ancieDt origin, and more or less con- 
nected with the traditions of almost all nations. It assumes 
that there exists within the earth a vast mass of incan- 
descent fluid matter, the crust of which forms the habitable 
part of our planet, and this hypothesis has played a pro- 
minent part in many schemes of world-making that have 
long since been forgotten. At the close of the last and 
beginning of the present century, two rival schools of geology 
sprung up under the names of Wernerian and Huttonian. 
The founder of the first was the justly-celebrated German 
philosopher, Werner, belonging to the University of 
Freiberg. His leading doctrine was " that the order of 
position which rocks maintain with respect to the centre 
of the earth denotes the order of their formation, and 
that the present arrangement of the rocky strata had 
been chiefly effected by the action of water — the crystallis- 
ing process being afterwards induced by certain chemical 
afiinities and molecular changes amongst the particles of 
which they are composed." With Werner, geology as a 
science may be said to have commenced — that is, as a 
science founded upon observation and experiment derived 
from a careful examination of the structure, contents, and 
stratigraphical position of the rocks themselves. The second 
school originated with Dr James Hutton, born in Edin- 
burgh in 1726, and may be termed the Edinburgh school of 
geology. His well-known work on the Theory of the 
Earth" was published in 1795, the preparation of which is 
said to have occupied his attention for a period of more 
than thirty years. The Huttonian theory may be divided 
into two branches or series of suppositions not necessarily 
dependent upon each other. One branch of the theory 
assumes that the strata constituting the crust of the earth 
are, from the nature of their mineral structure and the con- 
stant operation of the agents to which they are exposed, 
liable to decay ; and that, by being worn down and trans- 
})orted to the sea, they furnish materials for new strata to 
be formed and afterwards elevated ; and that from the 
