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Art. XII . — Synoptical Table of the Formations of the Crust 
of the Earth , and of the Chief Subordinate Masses . By 
Aime Boue', M.D. Member of the Wernerian Society, &c. 
Hitherto no one having attempted to construct a general 
synoptical table of geology, I submit the following one to the 
attention of the public. Its design is to exhibit the science re- 
duced to its most simple terms, and to enable every one to con- 
template at a glance the principal geognostical facts ascertained 
by the labours of geologists. Although I have consulted all 
the most distinguished opinions on geological classification, still 
the present attempt, I feel, will in many respects be faulty ; 
and indeed the principal advantage it can claim, is its contain- 
ing the results of all my unpublished observations made during 
the last three years. Taking nature, and not theoretical ideas, 
for the basis of my classification, I find, in the presence and 
absence of stratification of mineral masses, two great natural 
divisions, from which I infer three kinds of formation, viz. the 
unstratified or Igneous Formation, the stratified or Neptunian 
Formation, and the formations where the igneous and aqueous 
agents have acted together. Although it would be out of place 
to state here all the facts which led me to such theoretical 
views, because these are given in my Essay on the Geology 
of Scotland, and my Memoir on Germany and France, pub- 
lished in the Journal de Physique 1822, Edinburgh Philosophi- 
cal Journal 1823, and Annales des Sciences Naturelles 1824 ; 
still I may be indulged by a brief statement of my views, this 
being necessary for the more clearly following the details in 
the Synoptical Table. 
1. All geologists who have had opportunities of examining 
burning and extinct volcanoes, agree in admitting the existence 
of extinct volcanoes, or of very anciently volcanised countries. 
2. The greater number of geologists, and especially those 
who have visited extinct volcanoes, believe in the igneous ori- 
gin of tertiary basalt, in the form of streams (coulees), beds, 
cones, and veines, and also that of trachyte. 
3. A good many distinguished geologists agree in consider- 
ing it as probable that the secondary or floetz trap rocks are of 
igneous origin, because these rocks agree in nature, position, 
and accidents, with basalt and trachyte. 
4. And lastly, The intimate connection of the porphyries with 
