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WRIGHT: A NEW THERMAL MICROSCOPE 



PHYSICS. — A new thermal microscope for the measurement 

 of the optical constants of minerals at high teinperatures. 

 Fred. Eugene Wright, Geophysical Laboratory. 



With this microscope (fig. 1) three optical constants — bire- 

 fringence, extinction angle, optic axial angle — of a properly ori- 



Fig. 1 



ented crystal plate can be measured accurately at any tempera- 

 ture between 10°C and 1200°C. Above 1200° the intensity of 

 illumination from the furnace itself is so great that it tends to 

 veil the optical phenomena produced by the polarized light waves 

 transmitted thru the plate. The thermal microscope consists 



