PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 726th meeting was held on May 24, 1913, at the Cosmos Club, 

 Vice-President Bowie in the chair; 33 persons present. 



Mr. C. G. Abbot presented a paper on Results of measurements of 

 solar radiation. The essential features of this paper are presented in the 

 article on The variations of the sun by Abbot, Towle and Aldrich pub- 

 lished in this Journal, 3 : 309-315. 1913. Messrs. Humphreys, Paul and 

 Hersey discussed the paper. 



Mr. A. W. Gray then spoke on The control of temperature in an elec- 

 tric furnace. After a brief review of previous experiments to secure uni- 

 formity of temperature in an electrically heated air column by using the 

 central portion of a sufficiently long tube and by crowding the windings 

 near places where heat was losf most rapidly, the speaker described a 

 development of the electric furnace. The independently heated end 

 plugs of the earlier pattern were retained; two concentric cylindrical 

 heaters of nichrome ribbon, wound longitudinally and separated by air 

 and asbestos, supplied heat uniformly for entire length of the interior. 

 The new winding distributes any irregularities in resistance in such a 

 way as not to affect the longitudinal distribution of temperature, is non- 

 inductive, limits difference of potential between adjacent windings to 

 drop occurring in a length of ribbon twice as long as furnace, limits to 

 this length the amount of ribbon that can be accidentally short-circuited, 

 and brings out both terminals of a heater at same end of furnace and 

 diametrically opposite. Lantern slides were presented showing results 

 under various conditions. A further improvement consisted in moving 

 heating coils of plugs to extreme ends of furnace, making it easy to 

 secure uniformity of temperature within a few tenths of a degree over 

 at least twice the length of the furnace. The paper was discussed by Mr. 

 "White as to point of highest temperature and mechanical details. At 

 10.00 p.m. the meeting adjourned. 



The 727th meeting was held on October 11, 1913, at the Cosmos Club, 

 Vice-President Bowie in the chair; 41 persons present. 



Mr. L. J. Briggs presented a paper giving the results of an investiga- 

 tion by himself and Mr. H. L. Shantz on The water requirements of plants. 

 The governing conditions determining the absorption of water by the 

 roots of plants, its translocation thru the stems, and its final evaporation 

 from the leaves were first discussed. Attention was directed to peculiar 

 structural modifications found in certain plants, which are apparently 



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