Baron Humboldt on Kock Formaticnis. 
position of rocks. Since, then, the most striking analogies of situa- 
tion, of composition, and of organic bodies contained in contem- 
poraneous beds, have manifested themselves in the two worlds, in 
proportion as we become accustomed to consider the formations 
under a more general point of view, even their identity becomes 
every day more probable. 
In fact, on examining the solid mass of our planet, we per- 
ceive that some of those substances with which oryctognosy (de- 
scriptive mineralogy), makes us acquainted in their individual 
capacities, are met with in constant associations^ and that these 
associations, which are designated by the name of Compound 
Bocks, do not vary, like organic beings, according to the diffe- 
rences of the latitudes, or of the isothermal lines in which they 
occur. The geognosts who have travelled over the most re- 
mote countries, have not only met in the two hemispheres with 
the same simple substances, quartz, felspar, mica, garnet or horn- 
blende ; but they have also found that the great mountain mas- 
ses present almost everywhere the same rocks, that is to say, the 
same assemblages of mica, quartz and felspar in the granite ; of 
mica, quartz, and garnets in the mica-slate ; of felspar and horn- 
blende in the syenite. If it has sometimes been thought at first 
that a rock belonged exclusively to a single portion of the globe, 
it has been constantly found by later researches, in regions the 
most remote from its first locality. We are tempted to admit 
that the formation of rocks has been independent of the diver- 
sity of climates ; that perhaps it has even been anterior to them, 
(Humboldt, Geographie des Plantes, 1807, p. 115.; Vues des 
Cordilleres, vol. i. p. 122). Rocks are found to be identical 
where organic beings have undergone the most varied modifica- 
tions. 
But this identity of composition, tins analogy which is obser- 
ved in the association of certain simple mineral substances, might 
be independent of the analogy of relative situation and of super- 
position. One may have brought from the Islands of the 
Pacific Ocean, or from the Cordilleras of the Andes, the same 
rocks which are observed in Europe, without his being permit- 
ted to conclude that these rocks are superimposed in the same 
manner, and that after the discovery of one of them it might be 
predicted "with some degree of certainty what are the other rocks 
