August 27, 1920] 



SCIENCE 



205 



A SIMPLE DEVICE FOR SHOWING BY A 

 HYDRAULIC ANALOGUE THE EFFECT 

 PRODUCED ON THE POTENTIAL 

 DIFFERENCE BETWEEN THE 

 TERMINALS OF AN ELEC- 

 TRIC CELL WHEN THE 

 CIRCUIT IS CLOSED 



The Lodge theoretical paddle wheel device 

 shown by Professor Kimball in Figs. 336 and 

 337 of his " College Physics " (ed. 1917) sug- 

 gested to the writer an arrangement which 

 would render possible an actual lecture dem- 

 onstration. 



Into the glass U-tube of Fig. 1 a stream 

 of water is injected at P. The water is re- 

 moved at the exits E and E', the sizes of 

 which may be controlled by adjustable pinch- 

 oocks C and C on the rubber tubes T and T'. 

 The " current " is controlled by the pinchcock 

 C" or one's fingers on the rubber tube T." 

 The inflow at I may be controlled by the 

 faucet to which the apparatus is attached. 

 When C" is closed, h represents the potential 

 difference on open circuit. Upon opening C," 

 level B falls and A rises : h' <h or the poten- 

 tial difference decreases when the circuit is 

 closed. 



My friend, Professor F. A. Saunders, has 

 modified the arrangement by placing the 

 water-spout at P' (Fig 2). This is an im- 

 provement from the pedagogic standpoint as 

 the source of gross energy in an electric cell 

 lies at the surface of separation between one 

 plate and the electrolyte. He also suggests 

 removing the injected water at but one point, 

 E" (Fig. 2). 



N'oRTON A. Kent 



Physical Laboratory, 

 Boston TJniversity 



THE AMERICAN METEOROLOGICAL 

 SOCIETY 



The second meeting of the American Meteoro- 

 logical Society was held at the Weather Bureau, 

 "Washington, D. C, on April 22, 1920. The at- 

 tendance was 40 to 50 at each of the two sessions, 

 held in the morning and in the evening. Pro- 

 fessor C. F. Marvin, chief of the TJ. S. "Weather 

 Bureau gave a short address of welcome, which 

 was followed by a program of 15 papers. Brief 



synopses of the papers and discussions were pub- 

 lished in the society's bulletin for May, 1920 (pp. 

 48-55) ; and the papers themselves or authors ' ab- 

 stracts are still appearing in the Monthly Weather 

 Review (issue shown in parentheses). The pro- 

 gram was as follows: 



* Temperature scales and thermometer scales: E. 



"W. "WOOLARD. (May.) 

 Shall we adopt a half-degree absolute centigrade 



scale instead of the Fahrenheit? Charles P. 



Marvin. (Not published.) 

 The physics of the aurora: W. J. Humphreys. 



(Abstract to be published.) 

 *The auroras of March 2S-S5, 19 SO: Herbert Ly- 

 man. (July (?).) 

 The most intense rainfall on record: B. C. Kadel. 



(May.) 

 *New aerological apparatus: S. P. Ferguson. 



(June.) 

 Temperatures versus pressures as determinants of 



winds aloft: W. E. Gregg. (Abstract, May.) 



* Daily wind charts for stated levels: C. LeRoy 



Meisinger. (May.) 

 Cloud base altitudes as shown by disappearance of 

 balloons and kites: O. L. Lewis. (July (?).) 

 *Cloud nomenclature: Charles F. Brooks. 



(July(?).) 

 *Some meteorological observations of a bombing 



pilot in France: Thomas R. Reed. (April.) 

 Project for local forecast studies: E. H. Weight- 

 man. (March.) (By title.) 

 Climatic conditions in a greenhouse as measured 

 by plant growth: Earl S. Johnston. (Ab- 

 stract, April.) 

 Modifying factors in effective temperature: An- 

 drew D. Hopkins. (April.) 

 Relation of rainfall to the grazing capacity of 

 ranges: J. Wakren Smith. (June.) 

 Separates have been or are to be made of those 

 starred, and may be obtained from the TJ. S. 

 Weather Bureau, Washington, D. C. 



The American Meteorological Society, the project 

 of which was announced in Science, just a year 

 ago (August 22, 1919, pp. 180-181), and of which 

 progress was reported (December 12, 1919, pp. 546- 

 547) and organization in December announced 

 (March 12, 1920, pp. 275-276), has grown with un- 

 expected rapidity to a membership of nearly 1,000. 

 Plans are being made for the organization of a 

 Brazilian division of the society, and it is prob- 

 able that a Pacific division will be organized when 

 the Pacific section of the American Association for 

 the Advancement of Science meets next summer. 



