CALCAREOUS CONCRETIONS OF KETTLE POINT 141 
CaCO; /- - - - - - - - - 88.42% 
MgCO; 5 : e : = = = = 2.99 
Fe,03 - - - - - - - - = O97 
Residue insoluble in HCl] (SiO,) - - - - 4.25 
Hydrocarbons (and H,O) - - : z Ei) 323 
99.60 
Fic. 6. Looking down on the concretion of Fig. 5; fractured surface shows con- 
centric structure, the radial arrangement of the crystals not conspicuous in the photo- 
graph. 
The powder from which this analysis was made was previ- 
ously dried at ordinary temperatures in a desiccator ; any residual 
water was driven off at the low heat used to expel the hydro- 
carbons. The latter cannot then be said to have been exactly 
determined, but they probably do not total less than 3 per cent. 
The shales round about were found by Hunt to contain 12.4 per 
cent. of volatile matter, presumably hydrocarbons.’ The appear- 
ance of the magnesian carbonate is to be correlated with the 
* Chemical and Geological Essays, p. 179. 
