PREFACE. 
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In presenting the result of my observations on 
Fichtelit I have found it often necessary to allude to 
several other fossil resins which are very similar to it. 
I have given a short historical notice of these, and 
have also alluded to the points which they possess in 
common; showing that some of them, which are now 
considered distinct, are probably identical in composition. 
I was unable to make any direct comparison of 
these resins with Fichtelit, for they are all very rare, 
and seldom found in large quantity. This fact prevents 
a careful revision of the subject of fossil resins by one 
person. 
These investigations were made during the winter 
of 1856—57 in the laboratory of Professor Liebig. To 
him I am not only indebted for the assistance rendered 
