888 Opinions upon Clay Stones and Concretions. {September, 
the spherical concretions greatly varies from that of a pea to 
those many feet in diameter, while they are intersected by the 
laminz of the original deposit. 
The stones of Imatra, which have attracted much attention 
and are like our clay dogs, have been studied by M. Parrot, who 
has ventured to classify the irregular shapes under the names of 
monotypes, ditypes, tritypes, tetratypes, pentatypes and poly- 
types. Hypotheses to explain these have been various; first 
comes the gyration theory, which is inadmissible ; the stalactitic 
theory explains them by infiltration, the vegetable theory regards 
them as fossil toadstools, another theory considers them as copro- 
lites, the animal theory, which M. Parrot defends, considers them 
as the remains of petrified animals similar to Meduse. . 
Bowerbank and Parkinson attributed many flints to a coralloid 
origin as being alcyonaria which had attracted silex and had been 
covered with a gray crust presenting no trace of organization, and 
that they had then been penetrated by chalcedonic flint, red or 
purple, which had replaced the molecules of the animal matter ® 
it decomposed. : ? 
In Vol. 1v, 2d series, Transactions Geological Society of Lot- 
don, Dr. Fitton, in his paper upon the strata below the chalk, 
says, “all stages of gradation can be perceived from distinctly 
separated concretions of stone to others so nearly uninterrupte? 
that the next step into perfect continuity can be easily Ss 
again he writes, “in all these cases the concretions yer 
been formed after the deposition of the sand which pent 
them, and probably beneath a great depth of compacted J 
rials. In such a mass, shut off from the free access of pe , 
change of temperature, there is no obvious reason for dist n 
of affinitits which maintained the original form of the co | 
nents, except the decomposition of the animal a it sie | 
remains diffused among the stony substances, yet and gravel | 
not only solid limestone, where nothing but loose sand and 9 
were before, but firm siliceous concretions pervading, d tha 
identified with the separated particles of the quartzos¢ oof BE 
the whole is nearly homogeneous. If the decompositio loog 
organized substances, continually acting throughout “ye a 
periods of time be not sufficient to produce the ae we 
effects, perhaps it may be supposed that electricity ye ee 
which sets free the elemeats and disposes them anew. 
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