66 GEOLOGY OF THE SECOND DISTRICT. 



may so term it, an a priwi prejudice ; one which is not hkely to yield, until after a full exami- 

 nation of the facts and phenomena which are to be observed in the region where this rock is 

 well developed. The principal hope which I have, therefore, of the general adoption of the 

 foregoing views, is, that geologists will give a full examination of it in the counties of St. 

 Lawrence and Essex, where the rock is so well exhibited in all those relations which I have 

 attempted to describe in the preceding pages. 



If the doctrine of the igneous origin of limestone is admitted, several inquiries appear to 

 receive a satisfactor}' solution. What, for example, can better explain the escape of carbonic 

 acid from the earth in those regions where volcanic action is in operation, than the hypothesis 

 that it is derived from limestone in a state of ignition ?* And when the escape is prevented 

 by confinement in cavities, how rational the supposition that it may, by its elasticity, occasion 

 earthquakes, and other analogous phenomena, which are so frequent in volcanic districts. 

 And besides this, may it not be supposed that, under some circumstances, it may be reduced 

 in mass to the state of calcium ; a state in which it would become a body quite as energetic 

 in the production of those convulsions, as the disengaged and condensed acid, so justly the 

 terror of all volcanic districts ? And still it appears, that when exposed to heat under suffi- 

 cient pressure, the whole mass may fuse, without losing its carbonic acid, and in that state 

 be forced upward to the surface of the earth, through fissures and rents in its crust. The 

 doctrine of the existence of metallic bases of potash and soda, long ago taught in the 

 schools of chemistry and geology, has received from many philosophers a ready assent. 

 This state of those alkalies, it is true, is hypothetical ; but how much more probable is the 

 existence of calcium, when so much of the material for furnishing it exists among the pri- 

 mary rocks, and which, from their location and connection, must be associated with them, 

 not only as it regards position, but with their original states and condition, and the action and 

 energetic forces to which they must all be equally exposed. 



It is unnecessary, in this place, to refer to the modern improvements in experimental 

 chemistry, in relation to the liquefaction and consolidation of carbonic acid, as striking illus- 

 trations of the force and power with which this gas expands, and the tremendous violence 

 which it exerts even in a small way, in order to show what would follow from its condensa- 

 tion in the interior of the earth. These facts are familiar to all who visit the laboratory of 

 the chemist. It is true, we have other agents, as steam, and the gases of various kinds, 

 which must necessarily be developed where intense forces are made to act and react on each 

 other ; but no view of the subject relating to volcanic action and that of earthquakes, so fully 

 recommends itself to the consideration of the geologist, as that which calls in the aid of heat 

 on hmestone, followed by the disengagement of carbonic acid, which, under many circum- 

 stances, would take place. If no way for escape was opened, and the mass remained under 



* " Carbonic acid gas is very plentifully disengaged from springs in almost all countries, but particularly near active and ejttinct 

 volcanoes. The Grotto del Cane, near Naples, affords an example ; and prodigious quantities are now annually disengaged from 

 every part of the Liinagne d' Auvergne, where it appears to have been developed m equal quantity from time immemorial" 

 Lyell's Principles of Geology, Vol. I. p. 417. 



