Preston : Lincolnshire Naturalists at Sciuithorpe. 1 1 1 



this Ammonite in the beds. It presents many features of great 

 interest. Its geological position has been mentioned and many 

 of its fossils given ; but its mode of origin is always a problem, 

 and causes a certain amount of doubt and difficulty. The lower 

 unweathered beds of the stone are blue and contain FeC0 3 , 

 whilst the upper and fully-weathered beds have the iron in the 

 form of peroxide (Fe 2 0 3 ). Also the fossils in the lower beds are 

 often changed into carbonate of iron, proving that the carbonate 

 is a subsequent addition to the original formation. Hence it 

 would appear that the rock, as originally deposited, was an 

 ordinary limestone, that subsequently, probably when buried 

 deep in the earth's crust, carbonate of iron (the soluble form of 

 iron) entered the bed and was deposited either directly or as a 



partial transference into the limestone ; and that upon elevation 

 into a position to receive atmospheric influences the carbonate 

 became changed into oxide, and the useful ore produced. The 

 programme of the day had included much fossil collecting in this 

 pit and the examination of some higher beds in the series, but 

 the continuous downpour of rain had made the pit impassible, 

 and work impossible, therefore it was decided to end the 

 excursion here. When, however, the returning party reached 

 Winteringham Road, a few of the hardiest enthusiasts decided, 

 notwithstanding the still pouring rain, to accompany Mr. Preston 

 and visit a fault in the ironstone at the Midland Ironstone 

 Mines, about a mile away. This geological feature well repaid 

 a visit. It is a normal fault striking across the ironstone in a 



1901 April 1. 



