104 Mr. Dana on the Analogies between the 
Art. XIV.—On the Analogies between the Modern Igneous 
Rocks and the so-called Primary Formations, and the Meta- 
morphic changes produced by heat in the associated sedimen- 
tary deposits ; by James D. Dana, Geologist re the late U. 8. 
Exploring Expedition. 
[Read before the Association of American Géologiats and Naturalists at Albany, 
April 26th, 1843, and published by their authority.] ; 
Tue conclusions to which I arrive in the remarks that follow, 
are the result of observations made by me in the course of the cruise 
of the Exploring Expedition. In illustrating the subject, I have 
_ drawn but little upon the facts of the Expedition, as these are by 
authority reserved for the government publications now in process 
of preparation. I would however state, to justify myself against 
the imputation of haste in my generalization, that the regions 
offered for examination during the cruise, were of varied charac- 
ter and unusual interest; that the Andes of Chili and Peru, the 
mountains and plains of Oration, the coral, basaltic and volcanie 
- islands of the Pacific, and the regions of sandstone, coal and ba- 
salt in New South Wales, and portions of New Zealand, have all 
contributed to these results, offering rocks for examination of all 
ages from the burning lavas and forming coral rocks to the deep- 
seated granite and the associated schists; and there are scarcely 
any of these different formations which re not furnish something 
in elucidation of the subject under discussion. This may possi- 
bly be deemed sufficient to acquit me of presumption if I dare to 
differ from some names high in authority. I would disclaim ever 
having been actuated by a desire to seek out novel facts or novel 
principles, being satisfied that the common things which meet 
the eye, are more replete with instruction than the unusual and 
strange which only create surprise. 
_ The principles in view bear upon the metamorphic theory of 
r. Lyell, and they have been deduced by comparing the Pluto- 
~ nic rocks—the various granites and associated schistose forma- 
tions—with igneous rocks of all ages down to the modern lavas, 
together with their effects upon sedimentary strata. It will hence 
appear that although I may dissent from some of Mr. Lyell’s 
views, I am still carrying out his grand fundamental canon, that 
existing causes explain past phenomena, than which nothing has 
done more to advance and elevate the science of geology. 
