APPENDIX—GEOLOGICAL SURVEY. 
455 
formed rocks beneath the waters of the sea, and over which 
stratified rocks have commenced to form, will part with their heat 
slowly. Kadiation, nevertheless, will take place and continue 
until these igneous masses are brought down to the tempera¬ 
ture of the strata into which they have been protruded. One 
of the effects of radiation here would be, to change slowly the 
character of those prior-formed aqueous rocks. Metamorphic 
action would be induced, and the result of this form of force 
would be the transformation of these rocks into rocks of a 
metamorphic character. Beautiful examples of such condi¬ 
tions are found in the strata of the Cornish mines. Several 
large masses of igneous or melted matter (now in the form of 
granite) have been thrust up through what was once fine sedi¬ 
ment, or sedimentary material of aqueous origin. These sedi¬ 
mentary or stratified rocks are now transformed by the heat 
radiating from these igneous masses in their midst into various 
forms of slate rock, or as the miners call it there, kellas. The 
degrees of transformation, even, can be traced from the points 
of contact away for considerable distance into the slate rock. 
In the gradual decline of the temperature of these igneous 
masses, there would come a time when they would fail to trans¬ 
mit a sufficient amount of heat to maintain the force of metamor¬ 
phic action in the surrounding rocks. The heat, which at first 
was generally diffused through the adjacent rocks, from the en¬ 
tire igneous mass, will now be confined mostly to these lines of 
fracture and dislocation, extending down into these masses, and 
through them opening communication with the heated interior. 
At this point we may look for another tranformation of force; 
for below the point of temperature at which metamorphic 
action ceases, water will find its way into these fractures and 
dislocations by its own force of gravity, and yielding more 
readily to the action of heat than rock or solid matter, it be 
comes the medium through which radiant heat and mechanical 
force act. 
At first water may be transformed into elastic vapor and 
wrought up to its highest tension. In this form its mechanic¬ 
al powers under pressure become such as will defy all calcu- 
