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IOWA ACADEMY OP SCIENCE 



axis being greater than the one at right angles to this in the 

 ratio of about 1.7 to 1. the values of b 1 /b 2 should come out a 

 constant, and the variation in the table is merely an indication 

 of the experimental errors. The ratio a^/a,, would not necessar- 

 ily be a constant, although it so proves to be within the errors 

 of the experiment. 



TELLURIUM. 



Conclusion. — The importance of a study of isolated crystals 

 has been pointed out and preliminary direct results on the re- 

 flecting power of a selenium and of a tellurium crystal have 

 been obtained. These results have supported the original con- 

 tention, and are, the writer believes, the first direct results pub- 

 lished for these two elements to show that they have different 

 reflecting powers. Heretofore these reflecting powers have been 

 determined from large polished mirrors of these elements, and 

 of course only one value for each element for each wave length 

 has been determined. Further work along this line is to be 

 done in the immediate future. 



Physics Laboratory, 



State University of Iowa. 



