684 



SCIENCE 



[N. S, Vol. XLII. No. 1089 



Experiments and Theory of Conical Horns; In- 

 struments for Measurements of Sound; An In- 

 strument for Finding the Direction of a Fog- 

 signal: A. G. Webster. 



The Biography of Alfred Marshall Mayer: Alfred 

 G. Maybe and Eobert S. Woodward. 



The Solar Badiation and its Variability: G. 0. 

 Abbot. 



The New Draper Catalogue: Edward C. Pickek- 



INGf. 



One of the largest pieces of routine work under- 

 taken at the Harvard College Observatory is the 

 New Draper Catalogue. Its object, primarily, is 

 to furnish the class of spectrum of all the stars so 

 far as they can be determined from existing 

 photographs. This classification was undertaken 

 by Miss Annie J. Cannon, in October, 1911, and, 

 by observations persistently maintained for four 

 years, this portion of the work was practically 

 completed, September 30, 1915. During this 

 period, she classified 233,050 spectra, thus cover- 

 ing the entire sky. Meanwhile, 196,768 of these 

 stars have been identified, and 194,820 of them 

 entered in the card catalogue. The entire work 

 will fill nine of the quarto volumes of Annals of 

 the observatory, and will also give photometric 

 and photographic magnitudes of all the stars on a 

 uniform scale. 

 On the Albedo of the Moon and Planets: Henry 



NoRRis Russell. (Introduced by Edward C. 



Pickering.) 

 A Possiile Origin for Some Spiral Neiulce: 



George F. Becker. 



The paper seeks to show that the spiral, r°0" = 

 constant, is of use in interpreting the phenomena. 

 Concomitant Changes in the Earth's Magnetism 



and Solar Badiation: L. A. Bauer. (Intro- 

 duced by R. S. Woodward.) 



The author's preliminary conclusions respect- 

 ing appreciable changes in the earth's magnetic 

 state, concomitant with changes in the intensity 

 of solar radiation as shown by Abbot's solar-con- 

 stant values, are confirmed by a fresh investigation 

 based upon solar and magnetic data for 1913 and 

 1914. It is found, for example, that decreased 

 solar constant is accompanied by an increase in 

 the constant used to define, at any time, the 

 earth 's magnetic state, and by a decrease in the 

 range of the diurnal variation of the earth's mag- 

 netism. The numerical relationship between 

 changes in solar constant and magnetic constant, 

 or in the magnetic diurnal range, is shown to be 

 sufficiently definite to strengthen the conclusions 

 reached by Abbot respecting the sun 's variability. 



Diagrams were exhibited showing how, with the 

 aid of the relation found, certain puzzling fea- 

 tures respecting the secular variation of the 

 earth's magnetism and its so-called "non-cyclic 

 daily change," may be readily explained. 



Experiments on the Mean Free Path of Gases: 

 Observations on Wood's One-dimensional Gas: 

 Fred E. Wright and J. C. Hostetter. (In- 

 troduced by Arthur L. Day.) 

 In a paper on "One-dimensional Gases and the 

 Experimental Determination of the Law of Re- 

 flection for Gas Molecules, ' ' presented before this 

 academy at its April meeting, Professor R. W. 

 Wood directed attention to interesting phenomena 

 which he ascribed to reflection of mercury atoms 

 from an optically plane glass surface. Inspired 

 by this paper it occurred to us to apply Wood's 

 method to crystal plates and to ascertain if the 

 crystal symmetry aSeets the distribution of the 

 reflected mercury atoms. The experiments, with 

 the exception of two which yielded no results of 

 value, were all performed during the month of 

 May, but the publication of the results has been 

 postponed for reasons beyond our control. Our 

 preliminary results led at once to the construction 

 of a new piece of apparatus by means of which 

 evidence was obtained proving that a large part 

 of the phenomena are to be explained on the basis 

 of the kinetic theory of gases; they show that in 

 high vacua of pressures of only 0.2 bar there is 

 still sufficient gas present to inhibit the forma- 

 tion of ' ' one-dimensional gas. ' ' The experiments 

 illustrate, moreover, the change, with pressure, of 

 the mean free path of a given gas. Computations 

 on the basis of the kinetic theory are in agreement 

 with the experimental evidence and serve also to 

 explain the clear zonal ring of no reflection ob- 

 served both by Wood and by us. 



The Water Correction in Conductivity Determina- 

 tions: James Kendall. (Introduced by Alex- 

 ander Smith.) 



Conductivity water, however carefully prepared, 

 can not be kept for more than a few minutes in 

 contact with air without its specific conductivity 

 rising to about 0.9 X 10"' reciprocal ohms at 25° 

 C. This is the same as the calculated specific con- 

 ductivity of water saturated with carbon dioxide 

 under its atmospheric partial pressure (3.69 parts 

 in 10,000). It is therefore possible to eliminate 

 entirely the influence of the water in exact con- 

 ductivity measurements by correction for dis- 

 solved carbonic acid. This has been done for very 

 dilute solutions of strong electrolytes (Arrhenius), 

 transition electrolytes (Kendall), and weak eleo- 



