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re-action of silicate of manganese after blowpipe and spectro- 

 scope," and it is certain that the parent rock contains that 

 metal. Manganese in varying quantity is found throughout 

 the whole of the Middle Lias rocks, and it is not a little 

 remarkable that the deep sea dredgings of the Challenger 

 expedition brought to light large quantities of manganese rock 

 from different parts of the Pacific ocean. The next lithological 

 characters of the Spinatus sandstone to be mentioned are its 

 concretions, and these somewhat differ from what are generally 

 found disposed in courses through shales and clays. First, there 

 occur masses of mixed character, composed of small crystals of 

 Selenite, grouped around organic remains, such as osselets of 

 the Belemnite or other hard fossils; with some ochraceous 

 matter, the whole bound together by hydrated oxide of iron 

 into rough clump-like masses of utterly irregvdar shape, 

 varying in colour from light yellow ochre to a deep dark red, and, 

 of course, very dense in gravity from the large per-eentage of iron 

 in its composition. The concretions proper differ considerably, 

 none are of large size, not exceeding the bulk of a walnut. 

 Many consist of a cream coloured calcareous matter, without a 

 nucleus, these could not have been deposited from a solution of 

 lime, and were therefore particles of hme drawn from the sea 

 water by vegetation. Their immediate derivation is from 

 decomposed nullipores or other marine crustaceous plants 

 belonging to an order found in all parts of the Ocean, and 

 are much more numerous in warm than in cold climates: 

 under the action of a tropical sun, they lend themselves to rapid 

 decay and disintegration. Other small nodules require a notice, 

 as they attract our attention in breaking up the Sandstone. 

 These also are white concretions, irregularly dispersed, but 

 very hard from containing in addition to lime, some siliceous 

 matter and also calcic phosphate. When opened with a sharp 

 application of a hammer, they disclose a hard phosphatic 

 interior of dark smoky colour ; which, looked into with a lens, 

 are seen to be studded with tiny white seedlike bodies, of regular 

 oval form ; these are microscopic Crustacea of the division 

 Entomostraca. The white bodies of recent Ostracods when 



