Clay Concretions of the Connecticut River. 239 



a money bug, boot, arrow-head, geometrical figures, a seal 

 goose, fish, rooster, elephant, bird and a baby. 



Prof. Hitchcock speaks of receiving a concretion from an 

 able English geologist labeled, "Kimmeridge Coal Money 

 (use and age unknown), found abundant in the Kimmeridge 

 clay, Dorset coast— supposed turned in a lathe, and ancient- 

 ly used as money." 



Three questions must be asked : How does the com- 

 position of a claystone differ from that of the surrounding 

 clay, and is this composition definite ? 



What first determines the formation of a concretion ? 



What are the favorable and adverse conditions of which 

 I have spoken ? 



Chemical analyses answer the first question by the 

 following results : 



Deerfield claystone (opposite Whitemore's ferry), con- 

 tains, beside clay and iron, 42 p.c. carbonate of lime 

 (Ca CO,). Clay immediately surrounding claystone, 2-3 

 p.c. carbonate of lime. Claystone from south of Sunderland 

 bridge, west shore, 43 p.c. CaCO s ; surrounding clay, 2 p.c. 

 Brattleboro claystone, 42 p.c. Ca C0 3 . Hartford claystone, 

 41 p.c. Ca CO,. 1 



The essential difference, therefore, between the clay and 

 claystone, is the almost entire absence in the former of 

 calcium carbonate. These figures show that the composi- 

 tion of concretions is not definite, although it does not vary 

 greatty. We may say that nearly half a claystone is car- 

 bonate of lime, and as this is the active agent in the process 

 of formation, we can appreciate Le Conte's appellation of 

 " lime balls " in place of the popular name of " ckys tones." 



The second question is much more difficult to answer. 

 It requires the proof of the existence or non-existence of a 

 nucleus. It has been generally believed that these nuclei 

 exist. Prof. Hall, in the Geological Report of New York, 

 speaks of concretions having for a nucleus either a gravel 



1 Prof. Hitchcock gives four analyses thus: 42, 48, 49 p.c. Ca CO;;, and one from 

 Hadley which seems to be the exception to the rulej 56 p.c. Ca C03- 



