GEOLOGY. 245 



sea-water through a stratum of fragments of limestone that we must at- 

 tribute the production of the carbonate of soda, by which percolation, 

 probably, a partial interchange of elements has been effected between 

 the chloride of sodium and the carbonate of lime, giving rise to the for- 

 mation of chloride of calcium and carbonate of soda. It has been 

 long suspected that the natural production of carbonate of soda was 

 dependent on the presence of carbonate of lime, and was brought 

 about somewhat in this way ; but what the conditions are under which 

 the separation of the carbonate of soda from the chloride of calcium 

 is effected, without allowing the former to exert its ordinary converse 

 action upon the lime-salt and reproducing carbonate of lime, is a ques- 

 tion that would form a very interesting subject of scientific inquiry. 

 This is, I believe, the first time that the natural production of alkali 

 from sea-water itself, without organic agency, has been observed. 



Odor of Precious Stones. Fournet discovered that many precious 

 stones owed their colors to carburets of hydrogen. In 1855, J. 

 Schneider, by analysis confirmed this discovery. In a note recently 

 inserted in Poggendorff's Annalen, Schneider calls the attention of 

 mineralogists to the empyreumatic odor which certain forms of quartz 

 and granite give forth when rubbed. He thereby perceives the indi- 

 cation of the presence of organic matter or a carburet of hydrogen. 

 Cosmos. 



Cavities in Precious Stones. Sir David Brewster, in a paper re- 

 cently read before the Royal Society of Edinburgh, gives a brief ac- 

 count of the various phenomena of fluid and gaseous cavities which he 

 has discovered in diamond, topaz, beryl, and other minerals. He 

 describes : 



1. Cavities with two immiscible fluids, the most expansible of which 

 has received the name of Brewstolyne, and the most dense that of Cryp- 

 tolyne, from the American and French mineralogists. 2. Cavities con- 

 taining only one of these fluids. 3. Cavities containing the two fluids, 

 and also crystals of various primitive forms, some of which melt by heat 

 and recrystallize in cooling. 4. Cavities containing gas and vapor. 



The author states that the first class of cavities exist in thousands, 

 forming strata, plane and curved, and intersecting one another at vari- 

 ous angles, but having no relation to the primitive and secondary planes 

 of the crystal. From these facts, he draws the conclusion that the 

 minerals which contain them are of igneous origin ; and he considers 

 this conclusion as demonstrated by the existence of what h.e calls pres- 

 sure cavities, which are never found in crystals of aqueous origin. 

 These microscopic cavities, which are numerous in diamond, exist also 

 in topaz and beryl. The gas which fills them has compressed by its 

 elastic force the substance of the mineral around the cavities, as shown 

 by four sectors or quadrants of light which it polarizes : consequently 

 the mineral must have been in a soft or plastic state by fusion when it 

 thus yielded to the pressure of the included gas. 



Localities of Primoidial Fossils. The localities of primoidial fos- 

 sils in Europe, according to Mr. Marcou, are restricted to two places 

 in Bohemia. In this country they have been found at Braintree, Mass., 

 St. Mary's Bay (Newfoundland), Georgia, Highgate, and Swanton, 

 Vt, the vicinity of Quebec, and in Tennessee. In Vermont he had re- 

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