56 SCIENCE PROGRESS. 



It remains to be inquired whether such action results in the 

 formation of dolomite. This is not a very easy point to 

 settle decisively, but Klement came to the conclusion that the 

 product resulting from his experiments was not dolomite 

 but a carbonate of magnesium alone (neutral but hydrated). 

 He was, therefore, compelled to suppose that there is in 

 nature, not only a formation of magnesium carbonate by a 

 process comparable with his, but further, a combination of 

 this product with the intermixed calcium carbonate to form 

 dolomite. 



The crux of Klement's theory is evidently in this latter 

 transformation. There seems to be no direct chemical 

 evidence that such a combination is possible under con- 

 ditions realised in nature, and the micro-structure of dolomitic 

 rocks does not seem to throw much light upon the question. 

 Our author points to the dolomitisation of crinoidal and other 

 organic bodies as evidence that the assumed combina- 

 tion does take place; but this would seem to prove too much, 

 for crinoids are undeniably calcite organisms. If calcite 

 ossicles of crinoids can be converted into dolomite, which 

 seems to be beyond doubt, we may ask why should not the 

 same transformation affect whole bodies of calcite-rocks, 

 and further, why cannot the process be reproduced in the 

 laboratory ? 



If the process of dolomitisation of a limestone is some- 

 thing quite independent of the accumulation of the rock, 

 it may presumably be brought about at any distance of time 

 after that accumulation. That it is sometimes lono; sub- 

 sequent is proved by its evident connection in various cases 

 with joints, faults, and other geological accidents which have 

 affected the solid limestone strata. Further, the process 

 seems in some cases to have been later than recrystalliza- 

 tion in the limestone, whether produced by metamorphism 

 or otherwise. This at least may be inferred from the 

 apparent fact that the dolomitisation seems often to have 

 spared the more coarsely crystalline parts of the rock. The 

 Cambrian limestones in New Jersey, recently described by 

 Nason (7), seem to illustrate this. While the general body 

 of these rocks is of magnesian limestone or true dolomite, 



