322 PETROLOGICAL ABSTRACTS AND REVIEWS 



wholly replaces augite, and the rock has a gabbroidal texture; in others 

 there are more acid phases, and the rock passes through quartz-dolerites 

 and diorites to granophyres and granites. All such departures are 

 thought to be due to post-injection into the cooling body, or pre-injection 

 into the intercrustal reservoir. The intrusive sills belong to one period 

 of injection, and all phases were completed within a relatively short 

 time. Disbelieving that the intrusion could have taken place at one 

 time, owing to the fact that the slabs of sediment maintained their 

 orientation, Du Toit thinks that they were injected progressively from 

 the summit downward to the base, a mode of injection which he describes 

 as decensional lit-par-lit stoping. 



Eggleston, J. W. "Eruptive Rocks at Cuttingsville, Vermont," 

 Amer. Jour. Sci., Vol. XLV (1918), pp. 377-410. Figs. 5. 

 The eruptive body at Cuttingsville, Vermont, is thought to be a 

 composite stock, all of the rocks presumably coming from a single magma. 

 Essexite was the earliest intrusion, and nordmarkite the last. Horn- 

 blende-biotite-syenite, pulaskite, foyaite, and sodalite-nephelite-syenite 

 probably came between these two in about the order given. The order 

 of intrusion of the dikes is likewise from basic to acid. Essexite- 

 porphyries were earliest, some of them perhaps apophyses from the 

 essexite body. Aplite came after nordmarkite, and between these there 

 were syenite-porphyries and pulaskite-porphyries. There are also dikes 

 of tinguaite and of camptonite. The descriptions are not always clear. 

 Thus under essexite it is said that the plagioclase ranges from Ab^Anj 

 to AbjAuy, but it is not stated whether this is zonal, whether two different 

 plagioclases occur in the same section (!), or whether the plagioclase 

 differs in different parts of the area. A system of classification unknown 

 to the reviewer is used, for the statement is made that "the abundant 

 plagioclase allies it [the so-called syenite] to monzonite, but the ratio of 

 dark siHcates to feldspar warrants the designation of the rock as a 

 hornblende-bio tite-syenite." When it is stated that the "pyroxene is 

 next to the feldspars in abundance," one imagines that it must be present 

 in approximately the same quantity, yet the amount of feldspar is given 

 as 90 per cent, sodaUte as 3 per cent, and nephelite 3 per cent, leaving 

 4 per cent to be divided among pyroxene, biotite, apatite, magnetite, 

 titanite, and possibly pyrite. The norm shows 2.35 per cent of corun- 

 dum, but no feldspathoid. With five good rock analyses and an analysis 

 of the hornblende, more carefully modal percentages would have been 

 very instructive. 



