72 DESCRIPTION OF THE STRATA. 



quarries and openings, near Castle Howard and in other places. In 

 some instances, particularly at the Malton quarry now mentioned, 

 the oolite seems to pass into the blue limestone; the latter retaining 

 something of the oolitic structure, but with the ova or globules few 

 in number, and frequently of an unusual size, approaching to that of 

 small peas. These large ova, Avhen broken across, present the ap- 

 pearance of concentric circles, with a minute hole in the centre; but 

 this hole, where the fracture is recent, is generally filled with a fine 

 powder. The blue limestone is clouded or intermixed with a grey 

 stone, which may be called sandy limestone; though, fi'om its arena- 

 ceous quality, it may perhaps be more properly termed calcareous 

 sandstone. There are large ova thinly scattered in this stone, as 

 well as in the blue limestone; and it is observable, that the colour 

 of the ova changes with that of the stone, with this difference, that in 

 the blue stone the ova are of a darker blue than their matrix, whereas 

 in the grey the ova are of a much lighter colour than the stone, being 

 of a dull or yellowish white. 



In other instances, this limestone occurs without any mixture of 

 ova; and it is often of a very fine grain, the fragments presenting a 

 smooth surface, with no vestige of sand. Some of this limestone may 

 be seen at Pickering. It also occurs in quarries near Castle Howard, 

 a little to the north-west of Whitwell ; and on the long narrow ridge 

 on which Dalby stands, not far from that hamlet; at both which 

 places it is burnt for lime. The prevailing, colour of the limestone is 

 light blue; but it is more or less clouded with light grey, with some- 

 times a yellowish or ferruginous tinge. 



At the last mentioned places, it is uncertain whether the blue 

 limestone can be said to be next the oolite or not, the latter being 

 entirely wanting; yet the limestone corresponds with that which im- 

 mediately succeeds the oolite at Pickering and Sinnington; besides, 

 the blue limestone near Castle Howard is in the vicinity of the oolite, 

 and may be presumed to run beneath it. 



