396 Scientific Intelligence. 



diffusivitj^ of the rock and the tendency of the particular mineral 

 to crystallize. So that we may often give a shrewd guess at the 

 size of the sheet from observations on the grain only at one side. 

 I hope to take up this matter soon. 



Geological Survey of Micliigan, Lansing, Mich. 



9. Les Roches alcalines caracterisant la JProvince petrograph- 

 ique d^ Ampasmdava ; by A. Lacroix. (Nouv. Archives du 

 museum d' histoire naturelle. 4th Ser., Tome I, pp. 152, pi. 10, 

 4°, Paris 1902, Fascicule I.) — This work is based chiefly on speci- 

 mens and observations collected by M. Villiaume, a colonial 

 official. It is divided into three parts, the first being a descrip- 

 tion of the geology and rocks of Nosy Komba, an island off the 

 northwest coast of Madagascar between the island of Nosy Be 

 and the bay of Ampasindava."^ In this portion are described 

 gabbros, nepheline syenites of various types, including dark basic 

 varieties passing into the essexites. They are accompanied by 

 acidic dike rocks, and there is described, in addition, the phe- 

 nomena of the contact of these intrusive masses, both exomorphic 

 and endotnorphic. The second part relates to the occurrence and 

 petrography of igneous rocks from portions of the mainland in 

 this part of Madagascar and from Nosy Be. In this are described 

 granites with soda amphiboles, pulaskite, nordmarkite and laur- 

 vikite types of syenites, essexites, quartz bostonites, camptonites, 

 phonolites, trachytes, monchiquites, ijolite, tinguaite, etc., etc. 



The petrography of these rocks is given with the care and de- 

 tail for which the author's works are so well known. A number 

 of analyses enhances the value of the memoir, which adds greatly 

 to our knowledge of this little known region. The appearance 

 of Fascicule II, containing chapter iii, giving the general con- 

 clusions and resume, will be awaited with interest by petrog- 

 raphers. l. v. p. 



10. Ueber mariupoUt^ ein extremes Glied der ElaeolitJisyenite ; 

 von J. MoEOZEWTCz (Tsclier. Min. u. Petro. Mitt. Band xxi, 

 s. 238, 1902). — On the north coast of the sea of Azov in Russia 

 lies an area of crystalline rocks which is being investigated by 

 the author. In the district of Mariupol a portion of this area, 

 between gneiss and granite and comprising about 10-12 square 

 kilometers, has been found to consist of eleolite syenite and pyrox- 

 enite. The investigation of this former rock shows it to consist 

 of 73 per cent albite, 14 per cent of neph elite, 7*6 per cent of 

 aegirite, 4 per cent lepidomelane and 1'6 per cent zircon. The 

 mass analysis gave the following results : 



SiOs ZrOa AI2O3 FesOg FeO MnO MgO CaO K2O NaaO H2O Sum. 

 62-53 1-08 18-72 3-26 0-34 0-16 008 0-54 0-79 11-77 0-68 = 99-95 



In this the relation K^O : Na^O : : 1 : 24. The texture is variable, 

 sometimes coarse, sometimes fine, and sometimes porphyritic. 

 The feldspathic components are set through with aegirite needles. 



* (Stieler's Hand Atlas gives Ampassandava.) 



