Andrew. — On the Clarendon Phosphate- deposits . 463 



running water, or spread over a land-area by torrential rains. 

 (a.) No traces of stratification, false bedding, ripple-marking, &c, 

 are to be found, (b.) The joints are poorly developed and not 

 at all distinct, (c.) No fossils whatever have been found. Of 

 course, many true sandstones do not contain fossils, but the Mill- 

 burn sandstone has been provisionally correlated with the "Hut- 

 chison quarry-beds, which in places contain a rich assemblage 

 of marine fauna," and this fauna the Millburn sandstone does 

 not contain, so far as is known at present 



2. Sandstones are relatively hard rocks, and offer great 

 resistance to the agencies of denudation : hence in horizontal 

 stratified rocks we find sandstone bands marked by terraces and 

 cliffs. The Millburn sandstone is extremely hard and compact ; 

 had it been laid down in Lower Tertiary times, as Professor 

 Park thinks, it' would now form prominent outcrops above 

 the limestone. Instead, we find " an interval of 120 ft. to 

 150 ft., apparently occupied by a sandstone ... its outcrop 

 being obscured by a heavy slope deposit." The two outcrops 

 that do occur are far indeed from being prominent. The Mill- 

 burn sandstone, then, does not form outcrops as it should do 

 supposing that it was formed in Lower Tertiary times. 



3. Glauconite-grains are fairly abundant in the sandstone. 

 A normal sandstone is laid down in shallow water on the margin 

 of a land-area, and does not often contain glauconite, which is 

 a mineral characteristic of deposits formed in deep water. On 

 the other hand, a small number of grains of sand may be carried 

 out to deeper waters, where coral mud is being deposited, ac- 

 companied by glauconite : this would form a limestone contain- 

 ing a small amount of silica and glauconite. 



4. At the Millburn quarry I found that the depressions of 

 the limestone are filled with brown sands, which are derived 

 from the weathering of the subjacent limestone. Water con- 

 taining carbon-dioxide has dissolved away the calcmm-carbonate 

 and left behind the insoluble quartz and glauconite, the glau- 

 conite gradually losing its green colour as it decomposes to form 

 ferric oxide. That these brown sandstones have been derived 

 from the weathering of the limestone is certain, for it is not 

 uncommon to find patches of green sand still undecomposed in 

 their midst, and the latter are undoubtedly formed from the 

 limestone. They are afterwards, I believe, cemented together 

 by iron-oxide, derived partly from the weathering of the glau- 

 conite, partly perhaps from ferruginous percolating waters. The 

 percolating waters of this district do contain iron, as is shown 

 by the occurrence of at least two ferruginous springs flowing 

 from beneath the basalt cap. 



