Ixvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Yallecas, near Madrid, where there can be no doubt that the new 

 mineral has been produced by silica, probably hydrated, brought 

 into contact with carbonates of lime and magnesia held in solution 

 in water by carbonic acid*. 



But in these instances, and in many of those pseudomorphous 

 silicates for the investigation of which we owe so much to W. von 

 Haidinger and Dr. Blum, where no doubt can exist that the con- 

 stituent elements have been dissolved in water, almost all the 

 evidence requires that very long periods of time should be taken 

 into account; and their mode of formation is scarcely compatible 

 with the speculation by which Dr. Sterry Hunt would derive them 

 from deposits in clear sea-water contemporaneously, or almost so, 

 with the growth of the earhest known forms of organic existence. 

 Moreover the very fact described by him, of the occurrence in the 

 associated beds of large and well- crystallized specimens of various 

 minerals, seems to teach that a very gradual and long-continued 

 action after the first deposition of the sedimentary material can 

 alone account for the phenomena. 



Let it be granted, however, that, under certain conditions, watery 

 solutions, aided probably by high temperature, have been instru- 

 mental in the production of some varieties of the silicates of magnesia, 

 lime, alumina, and iron, it is yet to be considered whether, in deal- 

 ing with the great masses of crystalline rock in which the same 

 minerals occur, we are not still justified in referring them to the same 

 more deeply seated and extensive agency which in so many parts 

 of the world is giving us the clearest proofs of the reaction of the 

 interior upon the surface of the globe. 



Our Foreign Correspondent, M. Daubree, already so distinguished 

 for his researches on metamorphism, has recently pubhshed the 

 results of his Synthetical Experiments on Meteorites, and has thus 

 brought before us, from an entirely diiferent point of view, an 

 inquiry into the nature and origin of the silicated magnesian rocks 

 and minerals. 



It should be premised that Patrin long ago (in 1809) directed 

 attention to the identity of composition of the meteorites with the 

 substances ejected from terrestrial volcanos ; and more recently 

 (in 1858) Von Eeichenbach boldly sketched out some of the con- 

 clusions now experimentally arrived at by Daubree. Comparing 

 the meteoric stones with dolerite, Eeichenbach showed that the 

 former contained very few substances which are not to be found in 

 the latter, and that the mineral species which are met with in the 

 meteorites occur, almost all of them, in the volcanic and plutonic 

 rocks of the globe. Hence, he continues, we must infer that deep 

 down under the volcanos there exist masses of the same material 

 as the meteorites ; and we may suspect that the interior of our earth 



■*^ A discussion of this case, and an elaborate account of the occurrence of 

 another hydrated silicate, that of zinc, which appears to have been deposited in 

 certain caverns since the time of ElepJias primigenius, &c. will be found in the 

 excellent ' Notes on the G-eology and Mineralogy of the Spanish Provinces of 

 Santander and Madrid,' by Dr. Sullivan and J. P. O'Reilly : WiUiams and 

 Norgate, 1863. 



