THE GEOLOGICAL MAP OF THE WORLD. 351 
forms which in Central Europe indicate Carboniferous, Triassic 
and Jurassic formations. 
In the Valley of the Missouri the forms of fossil Brachiopods, 
which in Europe characterize the Mountain Limestone, such as 
Producti, Athyris, Spirifer, etc., are found in some beds which 
contain at the same time some other fossils, of which the forms 
Allorisma, Solemia, Schizodus and Pleurophorus, indicate in 
Europe the Dyas (formerly improperly called Permian). Thus 
several geologists have ignored the existence of the Dyas in 
Nebraska, in Iowa, and in Illinois, and have sought to substitute 
for it a formation of passage that they name Dyaso or Permio- 
Carboniferous. 
In California the forms of Tertiary and Cretaceous fossils are 
mixed together in such a way that some refer some groups of rocks 
to the Cretaceous formation, while others regard them as of the 
Tertiary epoch. 
In Australia, some beds containing Carboniferous Brachiopods 
are found placed beneath and even alternately with coal containing 
a flora regarded in Yorkshire (England) as Jurassic. Finally in 
New Zealand, the formations called Secondary seem to be entirely 
obliterated ; and it has been necessary to unite some rocks in the 
same groups under the bizarre name of upper Palzozoic or lower 
Secondary, ignorant to which of the two to refer them; and of 
the upper Secondary or lower Tertiary. 
These examples show that our classifications and our laws are 
still imperfect, and also the progress there remains to be made in 
order to thoroughly know the history of the earth. The attempts 
at classifications of eruptive and stratified rocks; those, not less 
humerous, of the relative ages of interruptions in the deposits of 
Stratified rocks; the study of the breaks and dislocations which 
have taken place on the surface of our planet, and of the relations 
which may exist between the one and the other, are all premature 
attempts, and of doubtful value. Having a knowledge, not even 
very profound, of some localities, theorizers have launched into 
the midst of generalities the value of which is very debatable even 
‘ln the interests of geology. But as it is a quality of human nature 
of always wishing to theorize and to go from the particular to the 
general, and as we are always fond of simple explanations and a 
priori views, we easily fall into an admiration for all those who 
seem to unveil and render themselves masters of the secrets of 
