Geology and Natter at History. 343 



that have originated in Productus through JRichthofenia, a highly 

 modified sessile productid. 



Does progress lie along the path blazed by Steinmann ? 



c. s. 



9. Miner alien- Sammlung en. Ein Hand- nnd Hilfsbuch filr 

 Anlage und lnstandhaltung Miner alogischer iSammlungen; von 

 Wolfgang Prendler. I Teil. Pp. viii, 220, with 314 figures. 

 Leipzig, 1908 (VV. Engelmann). — This is the first part of a work 

 which is planned to aid those who are concerned with the instal- 

 lation of mineral collections. It gives, in connection with some 

 practical instructions in regard to the collection of minerals, a 

 clear and coucise summary of the crystallographic and physical 

 characters of crystals. A novel feature is the discussion of the 

 arrangement of the collections, as regards cases, methods of 

 arrangement, labeling, etc., which gives many useful hints not 

 often found in print. 



10. Jadeite from Upioer Burma. — Dr. A. W. G. Bleeck has 

 recently made a careful study of the occurrence of jadeite in the 

 Xachin Hills of Upper Burma, and has presented some important 

 points in regard to the origin of this much discussed mineral. 

 It is found at three places, viz.: Tawmaw, Hweka and Mamon, 

 of which the first named is the most important and interesting. 

 The jadeite there occurs in a dike of igneous origin which is 

 intrusive in serpentine, the predominant rock of the plateau. 

 Besides the discussion of the properties of the mineral itself, and 

 the species associated with it, the conclusions of the author are 

 presented as follows in regard to the question of its origin : "He 

 concludes that the jadeite is the result of the metamorphism of 

 an albite-nepheline rock originally forming the dike, both 

 minerals being found together with the jadeite at Tawmaw. 

 The change would be represented chemically as follows : 



NaAlSi0 4 (Nepheline)+NaAlSi q 8 (Albite) = 



'2NaAlSi 2 9 (2 Jadeite). 



"Under certain conditions of crystallization nepheline-albite 

 rock might form, while, under conditions of high pressure during 

 consolidation or after, jadeite, which has a much lower molecular 

 volume, would be produced, the residual molecule forming albite 

 or nepheline according to which molecule was in excess in the 

 original magma. In the neighborhood of Tawmaw occur various 

 crystalline schists which are intruded into by granite. The 

 granite is traversed by veins of aplite and pegmatite (products 

 probably of the same great eruption) and masses of crystalline 

 limestone are found associated with the granite rocks, containing 

 various minerals characteristic of contact-metamorphism. The 

 relations of the granite to the crystalline limestone in this region 

 are similar to those of Mandalay Hill, Sagyin, and Mogok in the 

 Ruby Mines district, where similar contact minerals, including 

 the different varieties of corundum, are found in the metamor- 

 phosed limestone. The crystalline schists include chloritic schists 



