44 PROCEEDINGS OF THE PRINCETON MEETING 



found in a different order (especially Order 4 instead of 5), and even class 

 (II instead of III), than as an intrusive \A'ithout magmatic differentiation. 



Presented by title in the absence of the author. 



CHANGE IN THE CRY ST ALLO GRAPHICAL AND OPTICAL PROPERTIES OF 

 QUARTZ WITH RISE IN TEMPERATURE 



BY FRED E. WRIGHT 



(Al)stract) 



A brief description of the metliods and results of measuring the change In 

 the crystal angles and the optical properties of quartz to 1,250° C, the purpose 

 of such measurements being to gather information on the character and order 

 of magnitude of the crystal forces themselves. A crystal may be considered 

 a system of forces which exerts a definite influence on any external system 

 of forces (as that producing light waves) with which it is brought in contact. 

 On heating the crystal slight changes are produced in the crystal system of 

 forces, and these in turn produce slight changes in second system. The equa- 

 tion expressing the relation between these slight (differential) changes in the 

 two systems is a differential equation which on integration states the relations 

 between the original system. The results obtained thus far on quartz were 

 presented briefly from this viewpoint. 



Presented in abstract without notes. 



Discussion 



Prof. O. C. Farrington asked Doctor Wright for his definition of crystal. 



Doctor Wright replied as follows: The term crystal was applied first by 

 the Greeks to clear quartz crystals on the assumption that such crystals had 

 been formed from water by the action of a "long and vehement cold," thus 

 producing a kind of ice which did not melt easily. 



MODE OF FORMATION OF CERTAIN GNEISSES IN THE HIGHLANDS OF NEW 



JERSEY 



BY C. N. FENNEB 



(AJ) Struct) 



- The paper relates to the structure and mode of origin of certain pre-Cam- 

 brian gneisses in northern New Jersey. A description is given of the field 

 relations in a certain area near Pompton, where favorable conditions for ob- 

 servation have been found. The structures shown here are believed to be 

 tj'pical for considerable areas in this portion of the State. Evidence is found 

 leading to the belief that the origin of the banded gneisses at this locality is 

 to be attributed to the injection of a thinly fluid granitic magma between the 

 layers of an original laminated rock, which carried large amounts of horn- 

 blende or biotite. Structures which still survive in the associated bodies of 

 granite indicate that the process of injection was carried on in a most quiet 

 and gradual manner, and possessed many of the characteristics of a substitu- 



