OOLITE. 65 



cliffs, instead of regularly inclined planes. The Howardian hills, 

 indeed, can scarcely be said to have any line of fronts, as they gen- 

 erally swell and fall by gentle undulations. Yet several projecting 

 points, from these hills, stretch into the vale of York; and the ap- 

 pearance of some of these points exhibits a degree of regularity, ap- 

 proaching to that of the noithern oolite hills. 



In speaking of this chain as the oolite hills, we do not mean to 

 intimate, that they are wholly or principally composed of that kind 

 of rock ; but the name may be adopted, as the oolite forms a most 

 important feature in these hills, being the highest bed in the series of 

 which they are composed, and generally the thickest bed. This rock 

 is called oolite or egg-stone, as a great part of its substance consists 

 of minute globules, like small eggs, such as we see in the roe of a 

 fish; for which reason it is also called roe-stone. These globular con- 

 cretions are of various forms, being sometimes oval, though more 

 frequently round. They also vary in size, some being as large as 

 mustard seed, or even larger, while others are so minute that they 

 can scarcely be discerned by the naked eye. They are not petrifac- 

 tions, but have their origin in a pecidiar kind of crystallization; being 

 analogous to the large globules that appear in a variety of the Sunder- 

 land limestone, the crystalline structure of which is sufficiently obvi- 

 ous. Petrifactions, however, particularly shells, abound in the oolite 

 to a degree almost incredible; most of this bed appearing as? if it had 

 been composed of a mass of shells, having their cavities and inter- 

 stices filled up with the oolitic substance. Hence, as that substance 

 is more easily decomposed than the shells, the fronts of old quarries 

 in the oolite often present the appearance of grotto work, richly be- 

 studded with shells. 



The colour of the oolite is generally light grey, soinetimes ap- 

 proacliing to white, sometimes ash grey, and sometimes yellowish 

 grey. In some places we find patches or stripes that are blue, or 



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