438 ON THE GEOLOGY OF THE 



The ironstone which occurs along with this, is of no great 

 consequence, nor perhaps very general : it is not converted to 

 any useful purpose, so far as I could learn. 



There is another substance which occurs here and there 

 among the beds of the second limestone, analogous to the mu- 

 latto limestone of Antrim, which 1 believe to be a compound 

 of carbonate of lime and granular augite, similar to the coccolit 

 of Andrada, but much finer in the grain. In both, the colour 

 is dark green, and when the calcareous matter is separated by 

 means of acid, the coccolit remains in minute dark-coloured 

 grains. In Ireland, however, it occurs in more regular strata, 

 and of considerable extent, always under the white limestone, 

 and with the grains of augite pretty uniformly dispersed 

 through it. Here the beds appear to be mere adventitious 

 deposites, maintaining no conformity with the accompanying 

 strata, extremely irregular, and of small extent. Sometimes 

 they are entirely composed of the coccolit, when they are of a 

 very dark green colour, and very friable : in this state, the sub- 

 stance is used in the manufacture of Pigments. It is generally, 

 however, dispersed through the limestone, in which state it forms 

 a very beautiful rock. Here, as well as in Ireland, it usually 

 contains organic remains ; besides some bivalves, the belem- 

 nite the cornu ammonis, and the nautilus, are the shells which 

 I have generally seen in it. It assumes positions high and 

 low and may be considered an independent member of the 

 Second Limestone Formation. 



There is another variety of limestone, evidently of a subse- 

 quent date, which also occurs in this vicinity, but on so small 

 a scale, that it is scarcely deserving observation. In one place 

 only I noticed it on the road leading from Nice to Ville Franche, 

 where it lay in thick beds of a soft earthy texture, and con- 

 taining a quantity of vegetable remains. It is of a green- 

 ish-orey colour, and probably a species of calcareous tuiFa, 



which, 



