. Nature . e ulti-mate expression of metamorphism. It would be unfair, however, to judge the authorspowers of observation from this or by his morestartling propositions, such as that of the recon-stitution of sand-grains on p. 140. The fact that hehas seen so much throughout South Africa, in acountry laid bare by nature for the geologist, entitleshim to a serious hearing. The emphasis that he layson the descent of ore-material from the surface (p. 11),and on the ascent of calcium carbonate from below,recalls at once the tropical rains, and the pansupon the desiccating surface. But surely, as M
. Nature . e ulti-mate expression of metamorphism. It would be unfair, however, to judge the authorspowers of observation from this or by his morestartling propositions, such as that of the recon-stitution of sand-grains on p. 140. The fact that hehas seen so much throughout South Africa, in acountry laid bare by nature for the geologist, entitleshim to a serious hearing. The emphasis that he layson the descent of ore-material from the surface (p. 11),and on the ascent of calcium carbonate from below,recalls at once the tropical rains, and the pansupon the desiccating surface. But surely, as has lately pointed out in his Petrology,there is abundant evidence of the accumulation ofiron-ores under African conditions at the surface. Thewhole siliceous crust, however, according to , is a residue from the leaching-out and down-sinking of iron and magnesium from the primitivemeteoritic matter. The silica was first set free fromthis matter in a colloidal form which consolidated as. Bjulder in Dwyka Conglomerate, Prieska, illu>trating lateral flFrom Causal Geology. chert. Quartz arose only by metamorphic action inthe depths (p. 39J. When we are told that chert isnot crystalline, and when we reflect on the quartzdeposited in cavities from solution, as is the case inlimestones which retain all their fossils, we cannothelp thinking that our authors earlier studies havebeen temporarilv overcast by a cloud of careless writing of some sentences suggests thatthe work has been pushed forward with somethingof the heat of a new gospel. The word meteoriteis thus missing in the middle of p. 10; cubes of saltare said to be present (p. 57) in the bubbles ingranitic quartz ; to most field-workers the Archaeanmasses (p. 69) cannot seem characterised bv theenormous development of limestone; when carbondioxide is included in an analysis of the air, theomission of argon and its allies can hardly be excused(p. 93) by their minute proportions; Fig. .A,
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