250 Mr. De laBeche on theGeographicalDistrihutionof Organic 



produced by the rising of the aqueous vapours has ceased, 

 throw in another portion, and so on ; and keep the crucible, 

 when the whole mixture has been introduced, for about one 

 hour in a moderate red glowing heat (if the heat is too great, 

 it destroys the colour) ; when cold, pour water into the cru- 

 cible, and separate by means of it the brown residue of sul- 

 phur mixed with the ultramarine. A superabundance of sul- 

 phur may be expelled by a moderate heating. If the colour- 

 ing is not of an equal intensity, the most fiery ultramarine (and 

 this is a very important circumstance) may be obtained by 

 washing, and separating it from those parts which are less 

 coloured. From the component parts of the ultramarine as 

 given by the analysis, it cannot be formed, without a me- 

 dium. Thus this colour is nothing else than a siUcate of soda 

 dyed with sulphuret of sodium. 



!' The natural ultramarine contains a not inconsiderable 

 portion of potash and sulphuric acid ; and it is very probable 

 that the artificial production here mentioned may be usefully 

 varied, but this can only be discovered by experiment." 



XXXVI. Notes 071 the Geographical Distribution of Organic 

 Refuains contai?ied in the Oolitic Series of the Great London 

 a?id Paris Basin, arid in the same Series of the South of France. 

 Bi/ Henry T. De la Beche, F.E.S. S^c. 



[Continued from page 205.] 



Lovoest System. — Subdivisions; Cornbrash, Forest Marble, 

 and Great Oolite. 



XT has been considered that the former of these is a pro- 

 -* per subdivision, and may be traced to considerable di- 

 stances, but that the two latter may pass into or represent each 

 other. Great difficulty must always attend these minute di- 

 visions. Ml". Phillips gives only five feet as the thickness of 

 the cornbrash in Yorkshire ; it is represented as from eight to 

 sixteen feet in the neighbourhood of Telhsford and Farley 

 Castle, near Bath ; M. de Caumont doubts its existence in 

 Calvados, though there is a rock which M. Desnoyers and 

 myself consider may be referred to it ; and M. Boblaye men- 

 tions it in the North of France, but it does not so clearly ap- 

 pear to exist in the South of the same country. The forest 

 marble and great oolite seem to occur extensively. In Calvados 

 the latter, according to M. de Caumont, is intimately con- 

 nected with the inferior oolite. 



Mr. Phillips observes (Illustrations, &c. p. 158), "In the 

 midland counties, the fuller's earth rock of Mr. Smith does by 



no 



