PETROLOGICAL ABSTRACTS AND REVIEWS 255 



closely related to the tephrites of the region, and it is assumed that the 

 trachyte assimilated some of its constituents. The oldest and at the 

 same time most basic rocks of the region are the tephritic lavas. These 

 are followed by younger and progressively more acid noseUte-phonolite, 

 white pumice, and finally light trachyte. Among the ejectamenta 

 are fragments having the character of dike rocks, some of which are 

 more basic than the tephrites, and others more acid than the Dachs- 

 busch trachyte. Fragments of plutonic rocks, so far as these have been 

 analyzed, show intermediate chemical characters. The rocks are all 

 fully described and only lack estimates of the mineral percentages to 

 present good word-pictures of their appearance. 



Brauns, R. "Neue skapolithfiihrende Auswiirflinge aus dem 

 Laacher Seegebiet," Neues Jahrh., I (1917), 9-44. Pis. 2. 

 Nine more scapolite-bearing rocks from the Laacher Sea region are 

 described. There are many analyses, and a determination of the refrac- 

 tive index of the sulphate scapolite. 



Brauns, R. "tJber aufgewachsene Karlsbader Zwillinge von 

 Sanidin vom Laacher See," Neues Jahrb., I (1917), 45-49. 

 PI. I. . 



Brauns, R. "Einige bemerkenswerte Auswiirflinge und Ein- 

 schliisse aus dem niederrheinischen Vulkangebiet," Centralbl. 

 Min. Geol. u. Pal., 1919, 1-14. Fig. i. 



Brenner, Th. "tlber Theralit und Ijolit von Umptek auf der 

 Halbinsel Kola," Bull. Com. Geol. Finlande, No. 52, 1920, 

 1-30. Figs. 4. 

 Here are described the Kola Peninsula theralite, and a new ijolite 

 from the Tachtarwun Valley. The descriptions are elaborate and good 

 with the exception of the omission of an estimate of the mineral per- 

 centages in the theralite. Omissions of this kind lead to such errors as 

 the statement that "es giebt sowohl grobkornige, helle als kleinkornige, 

 dunkle Arten." But theralite is a name given by Rosenbusch to cer- 

 tain nephelite, plagioclase plutonic rocks which he thought were repre- 

 sented by certain tephrites and basanites described by Wolff from the 



