32 



c. From Wil lards' Ledge Quarry, Burlington, Vermont, 

 cutting the Potsdam sandstone. As shown in the sketch 

 exhibited, the dike was about 3 feet wide, but occupied 

 two parallel wedge-shaped cavities. 



A few other dikes of interest, from the same region, 

 are shown, with appended notes. 



I 



MINERALOGY. 



In Charge of George F. Kunz. 



MiNERALOGicAL APPARATUS recently acquired by the Min- 

 eralogical Department of Columbia University. 



1. FuESS Microscope with simultaneously rotating nicols. 



2. Seibert LiTHOLOGicAL Microscopes ; A, 11. 



3. Klein's Universal Rotation Apparatus for Crystals, 



especially for determination of optical principal sections 

 and measurement of angles between optic axes in liquids 

 of high index of refraction. 



4. Klein's Universal Rotation Apparatus for Thin Sec- 



tions, especially for exact orientation of haphazard sec- 

 tions and determination of their optical constants. 



5. Traube's Apparatus for darkening field of goniometer. 



6. Laspeyere's Burner for monochromatic light. 



7. Lamp for goniometer. 



8. Attachment for Converting Fuess goniometer into an 



axial apparatus. 



9. Attachment for Deliquescent Crystals, Fuess goni- 



ometer. 



10. Von Federow Mica Wedges for measuring strength of 



double refraction. 



