Dr Boue on the Formations of the Crust of the Earth . 131 
granite, syenite, and other unstratified rocks, not only in na- 
ture, but also in position, has induced some geologists to con- 
sider these also as of igneous formation. 
All the stratified rocks, with the exception of those of the 
first class, called Primitive, (a name I do not admit as connect- 
ed with theory *), are generally admitted to be of Neptunian 
origin. These rocks are distinguished by their peculiar tex- 
ture, and by the imbedded crystalline minerals they contain, 
and which are foreign to stratified rocks. Although the strati- 
fied primitive rocks are placed under the head Neptunian, I 
consider them as Neptunian rocks which have been brought to 
their present state by the agency of heat, and that the imbed- 
ded minerals they contain were introduced among them by the 
action of some igneous power, as stated in the Edinburgh Phi- 
losophical Journal for July 1823, and Annales des Sciences 
Naturelles 1824. These stratified primitive rocks, then, are 
partly of Neptunian, partly of igneous formation. 
The tufaceous or conglomerated productions of ancient and 
modern volcanoes are more appropriately placed immediately 
after the igneous rocks, from which they are derived, than 
amongst the Neptunian rocks. 
Although the salt and gypsum deposites probably owe their 
origin to submarine solfataras, we have not separated them 
from the Neptunian series, because they were deposited by wa- 
ter. If these were removed from the Neptunian series, for the 
same reason we would be obliged also to separate from it masses 
of iron-ore, and of other ores, certain salts, &c. 
My theoretical ideas, already published, have induced me to 
separate from the Neptunian series the metalliferous veins, be- 
cause their contents are more easily traced to Plutonic than to 
Neptunian agents. 
The alterations occasioned in Neptunian rocks by their proxi- 
mity to those of igneous origin, are stated in the Table only in 
a cursory way, although phenomena of high interest. 
The Synoptical Table also presents the most striking zoolo- 
gical characters of each formation, the different periods of the 
appearance and disappearance of the different classes of vege- 
tables and of animals, and a proper selection of synonyms of 
the different denominations given to the rock formations. 
* We have prefixed the word Primitive to the first class for distinction’s 
sake — E dit. 
