572 DK. J. W. EVANS ON MECHANICALLY -FORMED [Aug. I9OO,. 



The presence in the rock of well-rounded quartz-grains less than 

 1 millimetre in diameter is strong evidence in favour of a subaerial 

 origin. Such grains are rarely if ever produced by river- or surf- 

 action, but are almost always present in wind-blown sand. 



Neither the fragments of igneous origin nor the rounded quartz- 

 grains have a coating of carbonate of lime such as they would have had 

 if they had been present in the saturated sea-water at the same time 

 as the organic nuclei of the calcareous grains. They must, therefore, 

 be additions to the materials of the rock, subsequent to the time 

 when those calcareous grains were removed from the action of sea- 

 water. This circumstance also disposes of any idea, if such were 

 entertained, that the envelope was deposited round the nuclei after 

 the formation of the rock by the action of percolating subterranean 

 water charged with carbonate of lime. What was then added was 

 merely the clear calcite- cement that binds the whole rock together. 



There are other points connected with the shape and state of 

 preservation of the foraminifera which support the view that these beds 

 were accumulated by the transporting action of the wind, but they 

 fall within the province of Mr. Chapman's paper: see pp. 584, 588. 



It may be objected that any theory which suggests a different 

 origin for deposits that resemble each other so closely as those of 

 Ras Abu Ashrin and Marbat can scarcely be well founded. It must 

 be remembered, however, that, although the source and mode of 

 formation of the grains in the two rocks is, according to the view 

 I have taken, identical, in the latter case they were laid down with 

 marine fossils in shallow water near the shore, and in the former 

 were thrown up as part of a sea-beach and subsequently transferred 

 by the wind to the position in which they are now found. 



Although there seems every reason to believe that the Junagarh 

 Limestone was formed by seolian action, considerable difficulties 

 arise, if we assume that the calcareous constituents were transported 



Limestones, which succeed the Cambridge Beds, although almost entirely of 

 organic origin, are singularly free from macroscopic fossils, especially the 

 lower half of the series Minute search for such fossils in hundreds of ex- 

 posures lias generally been without success Notwithstanding the absence 



of macroscopic remains the Montpelier Beds, which compose the lower 500 feet 

 of the White Limestones, arc almost entirely made up of foraminiferal remains 

 — Orbifoidcs, Nummulina, and Miliolidce — at the base, grading up into Globi- 

 gerinal deposits.' The author attributes the absence of ' macroscopic fossils ' 

 mainly to the great depth at which he believes the deposits to have been formed, 

 but he brings no evidence to support this view, which is inconsistent with the 

 character of the foraminifera stated to be present at the base of the Montpelier 

 Beds. In any case the same explanation is not available as regards these 

 limestones in Kathiawar. All our information as to the geology and physical 

 geography of this part of India negatives the idea of such a depression at so 

 recent a period. It is remarkable, however, that these two deposits, the Mont- 

 pelier Beds and the ' miliolite ' of Kathiawar, are both characterized by the 

 presence of Miliolidce and the absence of larger fossils. The possibility of the 

 former being of aeolian origin seems at least worthy of consideration. Some 

 of the Jurassic oolites which exhibit false-bedding and are remarkably free 

 from fossils larger than the oolite-grains may, not improbably, also have been 

 accumulated by the action of the wind. See p. 579 of this paper. 



