proceedings: philosophical society 205 



weights. The value for the electrochemical equivalent of iodine was 

 determined to be 1.31052 mg. per coulomb. The value of the Farady 

 (I = 126.92) is found to be 96,515. Value calculated from silver 

 (Ag = 107.88) is 96,494, whence, for general use, round number 96,500 

 is recommended. The paper was discussed by Messrs. Hersey and 

 Sosman. 



The 735th meeting was held on January 31, 1914, at the Cosmos Club, 

 Vice-President Eichelberger in the chair; 31 persons present. The 

 minutes of the 734th meeting were read and approved. 



Mr. W. P. White presented a paper on Thermostats oj relativehj high 

 precision. By the aid of a few simplifying assumptions, it is possible 

 to give a very simple mathematical treatment of the ordinary mercury 

 contact thermostat. The results showed that, in general, an increase 

 in the precision of such a thermostat demands both an increase in the 

 temperature sensitiveness and a decrease in the temperature lag. Since 

 it is rather difficult to increase the sensitiveness and at the same time 

 diminish the lag, it will be desirable to reduce as much as possible the 

 heating rate, since this diminution diminishes the temperature lag. 

 In many cases, a rather elaborate procedure in this direction may be 

 the simplest way of increasing the precision. Some special devices 

 which tend to obviate the difficulties encountered in the ordinary type 

 of thermostat were mentioned. The paper was discussed by Messrs 

 Miller and Gray. 



Mr. F. E. Wright presented a paper on The measurement of crystallo- 

 graphic and optical properties at high temperatures, illustrated by an ex- 

 hibition of instruments. The basis of crystallography is the law, dis- 

 covered in 1669 by Steno, of constancy of angle between crystal faces. 

 The methods developed arose from consideration of possible changes 

 in crystal angles with temperature changes. The furnace used for 

 heating crystals and appurtenances were described. The cleavage 

 angle of calcite changes one degree between 0° and 575°, the change being 

 practically linear. Quartz shows much less change, about 11' in the 

 same temperature range; above 575° rate of change is rather less. Opti- 

 cal properties were also examined at different temperatures. Furnace 

 attachment to regular microscope was described and exhibited. The 

 paper was discussed by Messrs. White, Bowie, Priest, Burgess, Briggs, 

 Agnew, Miller, Coblentz, and Fenner. 



The 736th meeting was held on February 14, 1914, at the Cosmos 

 Club, Vice-President Eichelberger in the chair; 25 persons present. 

 The minutes of the 735th meeting were read and approved. 



Mr. H. H. Kimball presented an illustrated paper on The relation 

 between the solar radiation intensities and the air temperatures for the 

 northern hemisphere. The speaker discussed the marked diminution in 

 the intensity of direct solar radiation following the eruption of Katmai 

 Volcano in June, 1912. There was an increase in the quantity of heat 

 received diffusely from the sky, but the net result was a decrease in the 



