PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 787th meeting was held at the Cosmos Club, March 31, 1917. 

 President Buckingham in the chair; 36 persons present. The minutes 

 of the 786th meeting were read in abstract and approved. 



The following resolution was unanimously adopted: 



Resolved: That the Philosophical Society of Washington endorses the movement 

 to extend the use of the metric system and commends the efforts of the American 

 Metric Association to this end. 



Mr. Frederick Bates and Mr. F. P. Phelps gave an illustrated 

 paper on The rotation of the plane of polarization in quartz and iron at 

 high temperatures. 



Curves showing the results of precision measurements for both the 

 natural and the magnetic rotation of the plane of polarization in quartz 

 for a temperature range from 20°C. to 1000°( 1. were exhibited. Quartz 

 recrystallizes at about 575°C. changing from a to j3 quartz. The curve 

 for the variation of the natural rotation with the temperature makes a 

 right angle turn at this point and shows evidence of a discontinuity. 

 In contrast to the natural rotation the magnetic rotation shows no 

 change at 575° and has no temperature coefficient. For measuring the 

 rotations a large Weiss, water-cooled electromagnet was used. The 

 furnace was placed between the poles of the magnet and the temperature 

 was obtained by means of a standard thermocouple. Monochromatic 

 light of high intensity was passed through the plate parallel to the 

 magnetic field. Similar curves for the magnetic rotation in films of 

 electrolytic iron and iron oxides were also shown. The results indicate 

 that the optical phenomena disappear at the temperature at which the 

 metal loses its magnetic properties. 



Discussion. The paper was discussed by Messrs. White and Wright. 

 Mr. G. K. Burgess spoke of the possibility of harmonizing results show- 

 ing the magnetic rotation of films of iron which had become oxidized, 

 by disregarding the oxygen and considering only the iron present. 



Mr. F. E. Wright gave an illustrated paper on The application of 

 polarized light to the study of opaque substances. 



Mr. P. V. Wells gave an illustrated paper on A standard of turbidity. 

 The speaker described briefly the physical properties of turbid media, 

 pointing out that such media are usually in a critical state. Their 

 most striking characteristic is that of scattering light, the effect vary- 



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