ADDITIONAL NOTE ON CRYSTALS OF LAZULITE. 455 
limestone, yielding calcareous sediments (c).. These various sedimen- 
tary matters will be also in places more or less intermingled, pro- 
ducing rocks of intermediate or mixed composition. But these rocks 
will be shewn to be of the same period of formation, by the identity 
of some, at least, of the organic bodies enclosed in them. As recent 
formations, moreover (although many of the enclosed shells, &c., 
would necessarily be distinct, owing to the diverse nature of the 
Sediments, the more or less exposed character of the coast, the vary- 
ing depths of water prevailing at different parts, &c.,) we might 
expect to find in one and all, coins, pieces of pottery, and other ob- 
jects of human workmanship, proving their contemporaneous origin. 
Hence, the age of a rock is in no way indicated by mineral composi- 
tion: sandstones, limestones, &c., are of all geological periods. 
(5) From time to time, during the gradual deposition of these 
sedimentary formations, various eruptive rocks were driven up amongst 
them, producing (in general) chemical or mechanical alterations of 
greater or less extent. This action is still going on, as witnessed in 
volcanic phenomena. 
(To be continued.) 
ADDITIONAL NOTE ON THE CRYSTALS OF LAZULITE 
DESCRIBED IN THE JULY NUMBER OF THIS 
JOURNAL, PAGE 363. 
Since the publication of my remarks on the American variety of 
Klaprothine or Lazulite in the last number of the Journal, I have 
received a communication from Professor George J. Brush, of Yale 
College, New Haven, informing me that the crystals in question do 
not come from North Carolina, but from Georgia. They occur at 
