156 FIELD GEOLOGY. 



series of beds in each, we should be careful to speak of 

 them only as homotaxial and not contemporaneous. 



For instance, rocks in Bohemia and Scandinavia, con- 

 taining the same genera of trelobites as are found in our 

 lingula flags, have been correlated with them and with 

 one another, as if they were absolutely contemporane- 

 ous ; owing, however, to the above considerations this 

 cannot be regarded as accurately true, though it is cer- 

 tain that they occupy the same place in the geological 

 series of the several countries. 



From the preceding considerations we learn that 

 palseontological science, although so useful a hand- 

 maiden to that of geology, is not always to be implicitly 

 trusted in her guidings and indications. Geognosy, 

 though a more reticent, is perhaps a safer guide, when 

 her counsel is obtainable; but we should constantly 

 avail ourselves of the assistance offered by both on our 

 geological ways, and never lose sight of either except 

 where the exigencies of the road oblige us. 



