438 PETROLOGICAL ABSTRACTS AND REVIEWS 



Lacroix, a. Discours prononce a la seance de cloture du congres. 

 Congres des Societes Savantes a Paris, 1912. Pp. 20. 

 A study of the volcanoes of Madagascar. 



Lacroix, A. "Sur la constitution mineralogique des volcans de 

 I'ile de la Reunion," Comptes rendus, CLV (191 2), 538-44. 

 From a single volcano and a single magma there have been erupted 

 subalkaline and alkaline rocks, rocks which had long been considered as 

 necessarily having independent origins and localized in distinct regions 

 of the world (Atlantic and Pacific provinces). Nineteen analyses 

 are given. 



A. J. 



Lacroix, A. "Un voyage au pays des Beryls (Madagascar). La 

 Geographic," Bull. Soc. Geog., XXVI (191 2), 285-96. 

 A popular account of the minerals of Madagascar. 



Lacroix, A. Les riches ses miner ales de Madagascar. Conference 

 faiteal'EcoleColonialele 22 Dec, 191 2. Paris, 1913. Pp. 10. 



Leiss, C. "Ueber zwei neue Mikroskope fiir petrographische und 

 krystalloptische Studien," Zeitschr.f. Kryst., XLIX (1911). 

 Describes two new microscopes with nicol prisms connected by a 

 rigid bar. The first is after de Souza-Brandao and was originally 

 described and illustrated in 1903 in the report of the geological survey of 

 Portugal. Besides the attachments usual in a large petrographic micro- 

 scope, this instrument has a stage which may be tilted to any angle, and 

 an Abbe illuminating apparatus. The second, with a similar bar 

 connection, is after Wright, and was first described in 1910. In this, 

 likewise, the illuminating apparatus is after Abbe. A compensator 

 ocular is permanently attached to the tube. 



A. J. 



Leiss, C. "Neues petrographisches Mikroskop fiir die Theodolit- 

 Methode," Centralhl. f. Min., etc., 1912, 733-36. 



Describes a microscope which combines in itself a von Fedorow stage 

 and a petrographic microscope with simultaneously rotating nicols. 



