614 Reviews — B. Lindemann — Granular Carbonate Rocks. 



the general character and origin of the rocks and of their accessory 

 minerals. The second and last sections are briefly reviewed here. 

 Cotta held in 1827 that crystalline limestones might be either 



(1) original secretions of calcium carbonate from the fiery fluid planet 

 mass, like the plutonic crystalline schists ; (2) rocks independently 

 erupted from the earth's interior ; (3) altered compact (sedimentary) 

 limestones. 



The second or truly eruptive limestones were characterised by 

 their numerous inclusions of fragments of baked schist (or gneiss) 

 [such as ai"e common in the crystalline limestones of Ceylon — 

 however they got there] ; and by their wonderful close and intimate 

 relation to the schists or gneisses they are associated with. Later 

 on, in 1853, he abandoned the eruptive view and thought that such 

 limestones had been more softened by heat than the surrounding 

 rocks, and had thus been able to behave as eruptive rocks, and 

 force their way under the influence of pressure into the crevices of 

 the surrounding rock and even to form dykes and bosses in them, 

 and break across their foliation planes. Then followed a gradual 

 consolidation to a granular crystalline rock, accompanied by the 

 development of contact-metamorphic minerals. [This describes 

 with w^onderful exactness the sort of thing that seems to have 

 happened in connection with the crystalline limestones of Ceylon, 

 w^hatever their actual origin may have been.] 



Naumann, too, believed that crystalline limestones might have 

 consolidated from a state akin to fusion (" aus dem feurig erweichten 

 Zustande"). The * Neptunists,' on the other hand, thought that 

 crystalline limestones I'esulted from the alteration of organic 

 limestones by percolating w^aters which dissolved and redeposited 

 the calcite, and introduced other carbonates and silicates as well ; 

 and they ignored the possibility of contact-metamorphism. These 

 views seem to result from a confusion of the truly crystalline lime- 

 stones of the schists with the ordinary crystallisation and obliteration 

 of organic structure that has often taken place in sedimentary 

 limestones. 



At the present day a majority of geologists (Giimbel, Lepsius, 

 Vogt, etc.) ascribe the characters of crystalline limestones to 

 regional or dynamo-metamorphism ; some others, to the contact- 

 metamorphic eifects of intrusive igneous rocks. In regional meta- 

 morphism four factors are involved, viz., (1) water as a solvent, 



(2) high temperature, (3) mechanical pressure, (4) long-extended 

 time of action. [Certainly pressure alone appears to result in the 

 degradation of already crystalline limestones, as in Iowa, and not 

 in the development of a crystalline structure.] 



Vogt has attempted to separate regional from contact-metamorphic 

 crystalline limestones, on the ground of differences in mineral 

 composition and of certain peculiarities of structure. He thinks that 

 an interlocked or granulitic {verzahiten) structure is characteristic 

 of regional metamorphic limestones, and that it is wanting in almost 

 all that are of contact-metamorphic origin ; and further, that, in 

 consequence of this peculiarity, hardly any marbles save those 



