:6 



SCIENCE. 



[N. S. Vol. XXII. No. 549. 



of this application of the copper method, ex- 

 cept in cases of extreme necessity. There are 

 two ways of using copper as a water supply 

 disinfectant. One plan is to treat the supply 

 directly, in the reservoir if there be one, or 

 at the intake gallery if the water be drawn 

 from a lake or stream. In the latter case the 

 treatment necessarily must be continuous. 

 The second plan is to treat water before filtra- 

 tion. By the use of suitable chemicals, all the 

 copper is precipitated and removed from the 

 water by the subsequent filtration. 



Albuquerque, N. M., and Columbus, O., are 

 examples of the first plan of treatment. These 

 two cities greatly reduced the number of 

 typhoid cases during epidemic seasons, and the 

 chemical examinations that were raade failed 

 to show copper in the water drawn from faucets 

 of consumers. 



Anderson, Ind., is an example of the second 

 plan of treatment, and even with the filters 

 laboring under structural defects^ it seemed 

 possible to remove all bacteria usually sup- 

 posed to indicate sewage contamination. 

 Disease Resistance in Plants: W. A. Orton. 

 The Occurrence of Extractives in Apple Skin: 



Herbert C. Gore. 



Herbert J. Webber, 



Secretai'y. 



the philosophical society of WASHINGTON. 



The 603d regular meeting was held May 

 27, 1905. The evening was devoted to papers 

 on absolute electrical raeasurements with a 

 description of the experiments now in prog- 

 ress at the Bureau of Standards. 



Dr. K. E. Guthe spoke on the ' Methods and 

 Apparatus Employed in the Absolute Meas- 

 urement of Electric Current.' After a short 

 introduction regarding the purpose of absolute 

 electrical measurements, the speaker described 

 and discussed the different methods and appa- 

 ratus which have been employed for the abso- 

 lute measurement of an electric current and 

 — by the use of a known resistance — of the 

 electromotive force of standard cells. The 

 tangent galvanometer and similar methods 

 are based upon the knowledge of the hori- 



^ I am informed that these defects are now 

 remedied. 



zontal component of the earth's magnetic field 

 and this can hardly be determined more ac- 

 curately than to 1 in 2,000, except by the 

 most refined methods. The different forms of 

 current balance make use of the absolute 

 value of gravity. In the electrodynamometer 

 methods the preliminary measurements in- 

 clude the determination of the elastic proper- 

 ties of the suspension. The electrodynamom- 

 eter which is being constructed at the Bu- 

 reau of Standards was described more fully. 

 Finally the results obtained for the electro- 

 chemical equivalent of silver were compared 

 and the need for new determinations with 

 reliable coulometers pointed out. 



Professor E. B. Rosa presented ' The Meth- 

 ods and Apparatus Employed in the Deter- 

 mination of V, the Ratio of the Electromag- 

 netic to the Electrostatic Unit of Electrical 

 Measurement.' After a discussion of the 

 older work the apparatus now in use by the 

 speaker and Dr. Dorsey was described. A 

 rapidly charged and discharged spherical con- 

 denser is inserted in one arm of a Wheat- 

 stone bridge and the galvanometer deflection 

 brought to zero; the quantity which is regu- 

 lated by hand is the number of charges per 

 second.^ The resulting value of v seems to 

 lie between 2.9964 and 2.9968 X 10'" cm.-sec. 

 — a range of 1/5000. 



In the discussion that followed Dr. Bauer 

 put the precision of the determination of H, 

 the earth's horizontal magnetic force, at 

 1/4000; an 'instrument may be sensitive to 

 1/20000, yet differ from another by 1/500; 

 and Mr. Wead spoke of the disregard of the 

 masterly research of Cornu on the velocity of 

 light, in comparison with the results under 

 less widely varied conditions of the brilliant 

 American experiments. 



Charles K. Wead, 



Secretary. 



THE new YORK ACADEMY OP SCIENCES. SECTION 

 OF ASTRONOMY, PHYSICS AND CHEMISTRY. 



The regular monthly meeting of the section 

 was held at the American Museum of Natural 

 History, on Monday evening. May 15. The 

 papers presented were as follows : 



