154 H. ^ F. J. Warth—On Indian Later ite. 



greater contrast of colours. It is evident that great depth is not 

 absolutely necessary to the formation of manganese nodules, as the 

 Creechbarrow Beds, being associated with fresh- water limestone, could 

 not be other than shallow- water deposits, whilst the manganese 

 nodules from the bottom of the Pacific Ocean were formed in depths 

 between 2,500 and 3,000 fathoms. 



TJie Creechbarrow Limestone. — Perhaps the first stage in the 

 description of this curious rock should be an illustration of the mode 

 of its growth in the associated sands. This may be well studied in 

 No. 4 pit, where there were several calcareous nodules just under- 

 neath the irregular base of the great mass of limestone. The one 

 figured (Fig. 3, p. 153) may be deemed characteristic. 



Externally there is a kind of skin made up of very closely set 

 calcitic layers, which have a rough exterior and include a few 

 sand grains. The rest of the nodule consists mainly of carbonate of 

 lime with a small amount of very fine mechanical sediment. In 

 this respect it differs greatly from the manganese nodules, which 

 take up a large quantity of the sandy matrix. The concentric 

 character of this concretionary body is well shown towards the 

 exterior, and occasionally in the interior, but the general mass 

 is a rather light porous material with denser nests of calcitic matter 

 here and there. Some of the holes in the more porous parts are 

 suggestive of slender stems round which deposition in the first 

 instance has taken place, and the aspect generally may be described 

 as tufaceous. 



{To be concluded in the May Nnmher.) 



III. — Thk Composition of Indian Laterite. 



By H. Warth, D.Sc. Tilbiugeu, auci F. J. Warth, B.Sc. Lond. aud Birmingham. 



AFTER the appearance of Mr. T. H. Holland's paper on Laterite 

 in the Geological Magazine, February number (pp. 59-69), 

 we can at once give the results of our analysis of Indian laterite, 

 without further introductory remarks. They are as follows : — 



I. Pure Gibhsite from Kodihanal, previously recorded in the Minera- 

 logical Magazine, May, 1902. 



H3O 33-74 



Si02 2-78 



TiOs -04 



CaO" -20 



MgO -03 



FeoOs -44 



AI3O3 62-80 



100-03 



