488 PETROLOGICAL ABSTRACTS AND REVIEWS 



The rocks of Tahiti are almost wholly olivine basalts, some with nephelite or 

 analcite. Trachytic and phonolitic lavas occur on five of the seven islands. A 

 nephelite-latite, consisting of alkalic feldspar and andesine with some nepheUte 

 and sodalite and abundant hornblende, much titanite, and few augites and 

 micas is given the new name of tautirite, from the valley, Tautira, Taiarapu, in 

 which it occurs. The mode is not given but the norm contains Or 31. i, Ab 28.3, 

 An 13.3, and Ne 10.8. 



Jehu, T. J., and Campbell, Robert. "The Highland Border 



Rocks of the Aberfoyle District," Trans. Roy. Soc. Edinburgh, 



LII (1917), 175-212, figs. 10, pis. 6. 



A series of grits, shales, limestones, cherty shales, graphitic shales, and 



various igneous rocks, in places highly altered, extending from Stonehaven to 



Arran, is grouped under the term "The Highland Border Rocks." They are 



here arranged in two divisions. The sediments of the Lower Series are either 



Upper Cambrian or transitional between Cambrian and Ordovician, and are 



thought to have been deposited in clear water near the verge of sedimentation. 



The lavas indicate submarine eruptions. The Upper Series, which belong 



higher in the Ordovician, include limestones, hornblende- and chlorite-schists, 



and igneous rocks. 



JoHANNSEN, ALBERT. Essentials for the Microscopical Determina- 

 tion of Rock-forming Minerals and Rocks in Thin Sections. 

 Chicago, 1922. Quarto, pp. vi + 54, figs. 24, pis. 6, and a 

 folding table. 

 This laboratory manual contains practically all of the data originally pub- 

 lished in the writer's Determination of Rock-forming Minerals, and in addition 

 gives modes of occurrence and many more points of separation between similar 

 minerals. Only a few very rare species, such as johnstrupite, mosandrite, 

 laavenite, etc., have been omitted, but by uniting the tables which contained 

 minerals having birefringences greater or less than quartz, and refractive indices 

 greater or less than Canada balsam, much repetition has been avoided, and the 

 number of pages has been materially reduced. Orthorhombic minerals have 

 been united with the other biaxial minerals, since sections which cut all of the 

 crystallographic axes in this system show inchned extinction, but the extinc- 

 tion angles are given in the descriptions. The separation lines between the 

 various plagioclase feldspars have been changed from those given in the former 

 book to 5, 27I, so, 72^, and 95 per cent anorthite. Albite and anorthite have 

 been limited to a variation of only 5 per cent since these names are also applied 

 to the pure end members, and compound names, such as oligoclase-albite, 

 labradorite-bytownite, etc., have been omitted. The section on the deter- 

 mination of the feldspars has been but little reduced, but that on optical 



